Explanation:

A-S ; B-Q ; C-R ; D-R

The first stage of male–female recognition in flowering plants takes place when pollen lands on the surface of the stigma. In Brassicaceae, compatible pollen will hydrate and germinate, leading to successful fertilization, while these processes are severely impaired in incompatible pollen, preventing fertilization.
The radicle is the embryonic root of the plant, and grows downward in the soil (the shoot emerges from the plumule). Above the radicle is the embryonic stem or hypocotyl, supporting the cotyledon(s). It is the embryonic root inside the seed.
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In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center.