Q. Consider the following crops of India:
  1. Cowpea
  2. Green gram
  3. Pigeon pea
Which of the above is/are used as pulse, fodder and green manure? (UPSC Prelims 2012)

Answer: 1 and 2 only
Notes: While all three are biologically capable of serving those functions, the UPSC 2012 official key identifies [A] 1 and 2 only (Cowpea and Green Gram) as the correct answer. The distinction often lies in the "common agricultural practice" and "duration" of the crops in the Indian context:
Crop Pulse Use Fodder Use Green Manure (Standard Practice)
Cowpea Yes Yes (Excellent) Yes (Fast-growing/Succulent)
Green Gram Yes Yes Yes (Short-duration catch crop)
Pigeon Pea Yes Yes No (Usually too long-duration/woody)