A student observes that a popcorn kernel has a hard coat. He places the kernel in a moist paper towel and observes it for several days. He notices that the coat splits and a small root emerges. He concludes that

Water inside the seed coat creating a pushing force, breaking the seed coat.

Explanation:

Seed germination can be defined as the process by which a new plant emerge out from a seed. The radicle is the first emerging part from a seed and it develops into a root and the plumule is the second emerging part and it develops into a shoot. The light, water, adequate temperature, and soil are the factors that are necessary for seed germination.

According to a given situation, the popcorn kernel will receive the moisture necessary for the germination process, the water will imbibe into the seed coat creating pressure inside the seed and which will cause the seed coat to break and the new plant parts or seedling will emerge out of the seed coat.