Problem analysis: Analysis: First of all, we should make clear the names and functions of each part of the seed structure and the corresponding development relationship. Seed germination needs external conditions and its own conditions.

Answer: The process of seed germination: In the process of germination, the seed first absorbs water, expands in volume, and the seed coat bursts. At the same time, the life activities in the embryo began to be active, and after getting nutrition and energy from the cotyledons, they began to divide and grow: the radicle first stretched out to protrude the seed coat and developed into a root, and soon, some thin roots were born around this root; After that, the embryo develops into stems and leaves, and the hypocotyl develops into a part connecting the stems and roots.

So choose: a

Comments: Defining the seed structure and germination process is the key to solve the problem.