6.What is the permissible noise limit of 120 db?a) 30 minutesb) 2 minutesc) 1 minuted) 30 seconds7.Greenhouses gases causing a rise of 3℃ rise in the overall global temperature in the past century are CFCs. The CFC used in refrigerators isa) Ammoniab) Freonc) Methaned) Carbon dioxide8.In which layer of atmosphere ozone is very vital for all vegetation?a) Upper atmosphereb) Below atmospherec) Ground leveld) Below ground level9.Ozone can be destroyed by the following free radical(s)a) Chlorine radical (Cl)b) Hydroxyl radicals (OH)c) Nitric oxide radical (NO)d) all of these10.Which of the following is the oldest and the most common method used to dump the solid wastes?a) Riverb) Oceanc) Landfilld) None of the above11.Why is recycled paper banned for use in food containers?a) Because it creates a lot of spacesb) Because it creates contaminationc) Because paper can be used only one timed) Because paper is very thick and can’t cover the food containers12.What is called for a temporary hearing loss?a) Temporary ear painb) Temporary hearing problemc) Temporary threshold shiftd) Temporary hearing shift13.Which of the following sound is pleasant to our ears?a) Heavy machineryb) Transportation equipmentc) Loud noised) Music14.What is the dB of a threshold of hearing?a) 0b) 10c) 50d) 100​