self-pollination causes an increase in homozygosity in progeny in every generation of selfing up to approximately 96% in the F5, and selfing of homozygous line produce genetically similar progeny with negligible or little variability. So, the correct option is C. ( Yields progeny which are not genetically variable )

XX X Xx ...      Parents

I

XX Xx Xx xx ...     Fl hybrid

In Fl generation half of the total offsprings represent 
parental genotype i.e., Xx. Therefore out of 1200 seedling 600 will have parental genotype.

Cleistogamy is a type of automatic self-pollination of certain plants that can propagate by using non-opening, self-pollinating flowers. Since geitonogamy is the fertilization of a flower by pollen from another flower on the same (or a genetically identical) plant and geitonogamy is the fertilization of a flower by pollen from a flower on a genetically different plant and it is known that a cleistogamous flower is unable to pollinate via any of these methods. So, the correct option is "A" (Both geitonogamy and xenogamy are not possible).

Cleistogamy is the type of automatic self-pollination of certain plants. This is a form that is used to propagate plants by using self-pollinating flowers in bud state. This is also known as bud pollination.

•           Geitonogamy is the process for which the fertilization of a flower by pollen from another flower on the same plant.

•           Entomophily is the process in which pollinations are carried out by insects.

•           Xenogamy is the process of transfer of pollen grains to the stigma of a different plant. This process is cross-pollination.

Thus, the correct answer is option C.

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.