What I can think of is the cell genotype that stores nutrients in the seeds of corn B. The cells that store nutrients in corn seeds are endosperm cells, and endosperm is formed by fertilization of two polar nuclei and one sperm. Therefore, there is only one kind of dr in the egg cell and one kind of dr in the polar nucleus of maize B. It can be inferred that the plant of maize B has received the pollen DR of maize A, so the genotype of endosperm cells in the seeds of maize B is DddRrr.
There is a problem. Did you copy this question correctly? It seems that the process of hybridization between F 1 and corn C later does not help the final answer?