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Marble cancer is caused by Acid rain.

Parthenogenesis : In some organisms like rotifers, honeybees and even some lizards and birds (turkey), the female gamete undergoes development to form new organism without fertilisation. This phenomenon is called parthenogenesis.

(i) The inlets for air in stove get blocked which leads to yellow flame.
(ii) This problem is harmful for our environment as incomplete combustion results in the formation of oxides which are major pollutants of our environment.
(iii) For preventing this situation, gas or stove burners should be cleaned time to time.
(iv) Prudency, careful observation, decision making.

(i) In favour of negative response:
(a) It is used as a solvent in the manufacture of varnishes, etc.
(b) It is used in so many ways for medicines.
(c) It is used as a disinfectant.
In favour of positive response:
(a) Cause of death of many people.
(b) Many adolescents get affected out of it and become addicts, which affects their physical as well as mental health.
(c) Is being misused even where it is of important use (for example, painting shops, industries).
(ii) Initiatives:
(a) Drive to spread awareness.
(b) Skit/street plays/drama.
(c) Organising exhibitions.
(d) Organising debate.

Substance oxidised  :HCI
Substance reduced :MnO₂
Oxidising agent       :MnO₂
Reducing agent       :HCI

Nitrogen dioxide gas.

Correct answer is (d) 4

It indicates that the valency of lead in this case is 2 and it forms +2 ions.

Oxidizing agent: An oxidizing agent is an element that gains electrons. Since the oxidizing agent means to gain electrons; it is said to have been reduced.

The element which undergoes reduction (gets reduced) is called oxidizing agent.

For example: 2Mg + O₂→ 2MgO

In the given reaction, O₂ is reduced by losing oxygen atoms. Thus, O₂ is an oxidizing agent as it undergoes reduction.

Reducing agent: A reducing agent is an element that loses electrons. The reducing agent means to lose electrons; it is said to have been oxidized.

The element which undergoes oxidation (gets oxidized) is called reducing agent.

For example: 4NH₃ + 5O₂→ 4NO + 6H₂O

In the given reaction, nitrogen is oxidized to NO by gaining oxygen atom.

Thus, NH₃ is reducing agent as it undergoes oxidation.

(i) When potassium iodide is added to aqueous lead nitrate, it forms potassium nitrate and a precipitate of lead iodide which is yellow in colour.

The reaction that takes place is:

Pb(NO₃)₂ + 2KI → 2PbI + 2KNO₃

Note: The insoluble substance formed is known as precipitate.

Precipitate settles down at the bottom of the test tube.

(ii) The type of reaction is double displacement reaction or precipitation reaction.

Any reaction that produces a produces a precipitate can be called a precipitation reaction.

(iii) The balanced chemical equation is:

Pb(NO₃)₂ + 2KI → 2PbI + 2KNO₃

1. 20 cm 

2. 10 cm.

(1) Free vibrations and resonance:

(2) Forced vibrations and resonance :

(1) Free vibrations : A body capable of vibrations is said to perform free vibrations when it is disturbed from its equilibrium position and left to itself.

In the absence of dissipative forces such as friction due to surrounding air and internal forces, the total energy and hence the amplitude of vibrations of the body remains constant. The frequencies of the free vibrations of a body are called its natural frequencies and depend on the body itself.

In the absence of a maintaining force, in practice, the total energy and hence the amplitude decreases due to dissipative forces and the vibration is said to be damped. The frequency of damped vibrations is less than the natural frequency.

(2) Forced vibrations : The vibrations of a body in response to an external periodic force are called forced vibrations.

The external force supplies the necessary energy to make up for the dissipative losses. The frequency of the forced vibrations is equal to the frequency of the external periodic force.

The amplitude of the forced vibrations depends upon the mass of the vibrating body, the amplitude of the external force, the difference between the natural frequency and the frequency of the periodic force, and the extent of damping.

1. Avoid sex with a stranger/multiple partner.

2. Always use condoms during coitus.

True 

Acidity of a substance is measured with respect to the number of H⁺ ions it can generate. Acids that give rise to more H⁺ ions are said to be strong acids, and acids that give less H⁺ ions are said to be weak acids.

• In aqueous solutions strong acids ionise completely and provide hydronium ions. 
• On the other hand weak acids are partially ionised and an aqueous solution of same molar concentration provides a much smaller concentration of H₃O⁺ ions. 
• Strong acids — Hydrochloric acid, sulphuric acid, nitric acid
• Weak acid — Citric acid, acetic acid , formic acid

(i) When lead nitrate [Pb(NO₃)₂] is heated, it forms lead oxide. The emission of brown fumes is also observed. These brown fumes are of nitrogen dioxide (NO₂).

The reaction that takes place is: Pb(NO₃)₂ + heat → 2PbO + 4NO₂ + O₂ 

Lead nitrate lead Nitrogen Oxide dioxide 

The above reaction is an example of decomposition reaction in which single reactant breaks down to give simpler products.

(ii) When green crystals of ferrous sulphate [FeSO₄] are heated, the crystals lose water and the colour of the crystals changes. It then decomposes to ferric oxide [Fe2O₃], sulphur dioxide, and Sulphur dioxide.

The reaction that takes place is:

FeSO₄ + heat → Fe2O₃ + SO₂ + SO₃

Ferrous sulphate sulphur Sulphur dioxide trioxide

The above reaction is also an example of decomposition reaction

(a) NaHCO₃ .

(b) Na₂CO₃ .

Strong acids are those acids which are completely ionised in aqueous solution. Weak acids are those which do not ionise completely in aqueous solution. Strong acid: HCl, HNO₃,H₂SO₄ Weak acid: Citric acid, acetic acid, formic acid.

(d) Thyroid gland

Light green is the Colour of crystalline FeSO₄.7H₂O. Light green changes to reddish brown or brown upon heating.

(i) FeSO₄.7H₂O+heat → FeSO₄+7H₂O

(ii) 2FeSO₄+heat → Fe₂O₃+SO₂+SO₃

(c) Unicellular, sensory cells

(i) Indicators are the substances which change their colour in different types of substances.

(ii) Lichen.

(iii) Examples of natural indicators :

(a) Beetroot extract shows same colour in all sour substances and a different colour in bitter substances.

(b) Turmeric gives a yellow spot on a cloth but when washed with soap, the colour of the spot changes to red.

The basic principle behind getting relief from an insect bite is neutralization. The insect sting/bite may produce a secretion which is acidic or basic in nature. Based on that, one can choose basic or acidic substance so as to neutralize the effect. This way, less pain is experienced. Apply an alkaline substance if the sting is acidic and an acidic substance if the sting is alkaline (basic). 

For example, ant stings are acidic (methanoic acid). Hence it should be treated with an alkaline substance like baking soda.

The colour of FeSO₄.7H₂O crystals is light green. Upon heating the crystals of FeSO₄.7H₂O losses water of crystallization and becomes white in colour, Balanced chemical equation for the change is: -

2FeSO₄ Fe₂O₃ + SO₂ + SO₃

When an ant bites us, it injects formic acid into our skin. It causes pain and itching.

(c) elastic connective tissue

(d) Specialized connective tissue

Cartilage : The intercellular material of cartilage is solid and pliable and resists compression. Cells of cartilage (chondrocytes) are enclosed is small cavities within the matrix secreted by them. Cartilage is present in the tip of nose, outer ear joints, ear pinna, between adjacent bones of the vertebral column, limbs and hands on adults.

Bones : Bones have a hard and non-pliable ground substance rich in calcium salts and collagen fibres. Bones support and protect softer tissues and organs. Osteoblasts are present in the spaces called lacunae.

Blood : It is the fluid connective tissue. It contains RBCs, WBCs and platelets. It functions as a transport medium for nutrients, wastes and respiratory gases.

(c) Lichen,Answer is correct

1. When an ant bites it injects formic acid into the skin. 

2. Our stomach contains hydrochloric. 

3. When soil is acidic, it is treated with quick lime (calcium oxide. 

4. If the soil is basic organic matter compost is added to it. 

5. China rose indicator turns acidic solutions to dark pink (majenta) and basic solutions to green.

In this tissue, the cells and fibres are loosely arranged in a semifluid ground substances, e.g., fibroblasts, macrophages, fat cells and mast cells. Areolar connective tissue present beneath the skin acts as a support framework for epithelium. It acts as a reservoir of water and salts for the surrounding body tissues. Hence, these are called tissue fluid.

Adipose tissue is similar to areolar tissue in structure and function. It is located beneath the skin, surrounding the kidneys, eyeball, heart etc. Adipocytes store fat. It is called white fat. The adipose tissue which contains a lot of mitochondria is called brown fat or brown adipose tissue. Reticular connective tissue is filled with fibroblasts called reticular cells. These cells store fats and the excess nutrients.

1. Litmus is extracted from lichens. 

2. The solutions which do not change the colour of either red or blue litmus are known as neutral Solutions. 

3. The word acid comes from the Latin word acere. 

4. The chemical name of milk of magnesia is magnesium hydroxide. 

5. Sodium hydroxide or Pottassium hydroxide is found in soap.

• Fossils are remains of the plants and animals of the post geological age that occur in preserved form.

• Drug obtained from a gymnosperm - Taxus brevifolia and used for cancer treatment.

(a) A is correct R but is incorrect.

(b) juvenile phase, maturity phase, senescent phase

 Annual , biennial 

The mode of reproduction helps to introduce now variation in progenies through the combination of the DNA from 2 different individuals. These variations allow the individual to cope up with various environmental conditions and thus make the organisms better suited for the environment.

(a) Juvenile phase:

The period of growth is called the juvenile phase. It is known as vegetative phase in plants.

(b) Reproductive phase: 

The phase during which the organisms are able to produce their off springs.

(c) Senescent phase: 

The period during which the organisms loss their ability to produce their off spring.

⦁    असत्य
⦁    सत्य

देश की बहुपक्षीय प्रगति के लिए शिक्षा का अधिक-से-अधिक प्रसार होना अति आवश्यक है। इस तथ्य को ध्यान में रख़ते हुए राज्य द्वारा अनेक प्रयास किये जा रहे हैं। सर्वप्रथम हम कह सकते हैं। कि राज्य द्वारा शिक्षा के महत्त्व एवं आवश्यकता से सम्बन्धित व्यापक प्रचार किया जा रहा है। जन-संचार के सभी माध्यमों द्वारा साक्षरता एवं शिक्षा के महत्त्व का व्यापक प्रचार किया जा रहा है। इस उद्देश्य की प्राप्ति के लिए अलग से ‘राष्ट्रीय साक्षरता मिशन’ की स्थापना की गयी है। शिक्षा के व्यापक प्रसार के लिए भारतीय संविधान में 6 से 14 वर्ष के बच्चों के लिए नि:शुल्क तथा अनिवार्य शिक्षा का प्रावधान किया गया।
शिक्षा के प्रसार के लिए राज्य द्वारा ग्रामीण एवं दूर-दराज के क्षेत्रों में शिक्षण-संस्थाएँ स्थापित की जा रही हैं। शिक्षा के प्रति बच्चों को आकृष्ट करने के लिए उन्हें विभिन्न प्रकार के प्रलोभन एवं सुविधाएँ भी प्रदान की जा रही हैं; जैसे कि दिन का भोजन देना, मुफ्त पुस्तकें एवं वर्दी देना तथा विभिन्न छात्रवृत्तियाँ प्रदान करना। राज्य द्वारा अनुसूचित एवं पिछ्ड़ी जातियों के बालक-बालिकाओं को शिक्षित करने के लिए अतिरिक्त प्रयास किये जा रहे हैं। तकनीकी शिक्षा के प्रसार के क्षेत्र में भी राज्य द्वारा अनेक प्रयास किये जा रहे हैं। समय – समय पर राज्य सरकारों एवं केन्द्र सरकार द्वारा शिक्षा के प्रसार के लिए व्यापक अभियान चलाये जा रहे है; जैसे कि ऑपरेशन ब्लैकबोर्ड तथा ‘चलो स्कूल चलें’ आदि।

⦁    सत्य
⦁    सत्य

सही विकल्प है  (ग) सन् 1990-91 में

As we move down the group -15, the size of the element, increases and therefore the length of the E – H bond increases and its strength decreases. In other words, as we move down the group, the bond with hydrogen can break more easily to evolve H₂ gas. Which acts as the reducing agent. Thus Bi-H bond is the weakest amongst the hydrides of elements of group -15, and hence, BiH₃ is strong reducing agent.

1. Ranitidine is used as an antacid. 

2. Paracetamol is used to bring down the body temperature during high fever.

3. Tincture of iodine is used as an antiseptic. It is 2-3% solution of iodine in alcohol and water.

CO₂ is regarded as a hydride of carbonic acid.

Because H₂CO₃ → H₂O + CO₂

BiH₃, because the stability of hydrides decrease on moving form SbH₃ to BiH₃.