D.

Brassica

The occurrence of more than one embryo in a seed is referred as polyembryony. In many Citrus and mango varieties, some of the nucellar cells surrounding the embryo sac and develop into the embryos in such species each ovule contain many embryos (nucellar polyembryony).

C.

Cleistogamy

Bisexual flowers which remain always closed are called the cleistogamous and such condition of flowers is called cleistogamy. In such flowers, the anthers and stigma lie close to each other. When anthers dehisce in the flowers buds, pollen grains come in contact with stigma to effect pollination. Thus, cleistogamous flowers are invariably autogamous.

B.

grasses

Pollination by the wind (anemophily) is more common amongst abiotic pollinations. Wind pollination is quite common in grasses. 

B.

maternal sporophytic tissue in ovule

Substitution of usual sexual reproduction by a form of reproduction which does not involve meiosis and syngamy is called apomixis. In Citrus, apomictic embryo arises from diploid cells. (maternal sporophytic tissue) of the ovule occurring outside the embryo sac.

A.

embryo sac

In angiosperms, the unit of female gametophyte (embryo sac) is functional megaspore.