The condition of maturation of anthers and stigmas of the same flower simultaneously is
Geitonogamy: The transfer of pollen grains from the anther of a flower to the stigma of another flower borne by the same plant.
Xenogamy: Transfer of pollen grains from the anther of a flower to the stigma of another flower borne on a different plant but belonging to the same species.
Allogamy is the deposition of pollen grains from the anther of the one flower on the stigma of another flower, either in the same plant or in a different plant of the same species.
Homogamy: It is the condition in which flowers are bisexual anther and stigma mature at the same time to make self-pollination possible. Under this condition, the stigma receives the pollen grains from the anthers of the same flower by the agency of wind or insects.
So, the correct answer is D.