• India is densely and largely populated country. So, agricultural products are used extensively to feed the large population as well as raw materials in agro based industries.
• Moreover, 68.8% i.e. almost 70% of Indian population still resides in rural areas. This population is mainly dependent on agriculture. When these people cannot produce enough their income levels drop down drastically.
• So, they reduce their consumption i.e. they do not demand industrial products.
• The reduced agricultural production hits the industry in two ways
  1. First industries do not get enough raw material for production and
  2. The demand of industrial production reduces.
• Hence, we can say that failure of agricultural sector leads to failure of industrial sector.

Points for answer of other two questions:

• Since service sector cannot alone progress when the other two sectors fail, even the service sector will fall due to failure of agriculture.
• Hence, agriculture is backbone of our economy.