The plants receive Nitrogen in form of

The correct answer is B) Nitrate. Most crop plants absorb nitrogen from the soil through their roots mainly as nitrate ion (NO3-), which is taken up and moved to the shoot through the xylem. Plants can also take up ammonium (NH4+), but nitrate is the standard answer for this question.

• Ammonia (C): Ammonia is not the usual form in which plants draw nitrogen from soil. Ammonium formed from fertilisers or decomposition is quickly converted to nitrate by nitrifying bacteria (Nitrosomonas and Nitrobacter).
• Nitric oxide (A): NO is a gas formed in lightning and as an intermediate in denitrification. It is not a soil nutrient form that roots absorb.
• Nitride (D): Nitride ions (N3-) occur in compounds such as magnesium nitride. They are not the forms plants take up.

The concept is the nitrogen cycle, which is central to the Environment and Agriculture syllabus. Mains links include nitrate leaching into groundwater, neem-coated urea to improve nitrogen use efficiency, and the role of Rhizobium in legumes.

Trap: Aspirants pick ammonia because nitrogen fixation is often described as producing ammonia, or they assume plants absorb atmospheric N2 directly.