Pigeon Pea is . . . . . . . . crop.

Answer: Option D

Pigeon pea or red gram commonly called arhar is an important legume crop. Self-pollination is the rule in Red gram and natural crossing extends up to 65%, thus it is also known as often cross pollinated crop.
Often cross-pollinated species are those crop plants in which cross-pollination exceeds 5% and may reach 30%. Such species are generally known as often cross pollinated species means pollination occurs when pollen is delivered to a flower from a different plant.