The type of crop which is able to fix nitrogen from air is known as

Answer: (c) Legume

Legumes (pulses, peas, beans, groundnut) host Rhizobium in root nodules, which fix atmospheric nitrogen.

The idea

Because legumes carry nitrogen-fixing bacteria, they leave the soil richer than they found it. Farmers have used this for centuries by growing a pulse after a cereal.

Cereal crop takes nitrogen out of the soil → Next season a legume is grown → Its nodules add nitrogen → Soil recovers → The next cereal needs less urea

Why the others are wrong

(d) Wheat is a cereal — it takes nitrogen from the soil and needs fertiliser.

The trap

The word “legume” is the whole question.

Also know

The legume family includes all pulses (gram, arhar, moong, urad, masoor), groundnut, soybean and fodder crops like berseem. Legumes ploughed back into the soil are green manure: dhaincha and sunn hemp. India is the largest producer and consumer of pulses.