The correct option is
D Cross pollination by wind
Maize which is also known as Corn plant is pollinated by wind. The anthers are born in long tassels that move with the wind and shake off their pollen. The stigma is feathery and hairy so as to catch the wind-borne pollen. Thus, in maize, pollens are transferred from the anthers of one plant to the stigma of another plant by means of wind i.e. cross-pollination occurs by the wind.
So, the correct answer is B.