Option B is correct, dichogamy means production of unisexual flowers.. soo it shows cross pollination.. clestarogamy occurs only in clestarogamus flower(petals are always closed).. soo it contains self pollination.. homogamy means.. develepe ment of both male and female sex organs at Same time..it shows self pollination..

Dichogamy causes cross-pollination.

Explanation:
Dichogamy is a mechanism of flowering, where male and female reproductive structures do not mature at the same time. This phenomenon is observed in many plant species and can be further classified into two types:

1. Protandry: In this type of dichogamy, the male reproductive organs mature first, followed by the female reproductive organs. This ensures cross-pollination, as the pollen from the male flowers is transferred to the female flowers before the pollen is released from the female flowers.

2. Protogyny: In this type of dichogamy, the female reproductive organs mature first, followed by the male reproductive organs. This also ensures cross-pollination, as the pollen from the male flowers is transferred to the female flowers after the stigma has become receptive.

Dichogamy is a common mechanism of cross-pollination in many plant species, as it ensures that the pollen from one plant is not transferred to the same plant, thus promoting genetic diversity. Homogamy and cleistogamy, on the other hand, do not involve cross-pollination. Homogamy is the phenomenon of self-pollination, where the pollen from the same plant is transferred to the same plant. Cleistogamy is a mechanism where the flowers do not open, and pollination occurs within the closed flower.