Most Plants, Including Rice, Can Make Their Own Vitamin A

Most plants, including rice, can make their own vitamin A, but rice seeds cannot. Why not? What's the problem?

A) They don't have the genes to make the enzymes that make vitamin A.
B) They don't have the base pairs necessary to make vitamin A.
C) They have the right enzymes to make vitamin A but lack the genes.
D) They have the right genes to make the enzymes to make vitamin A, but they're inactivated.
E) The rice seeds are not mature enough to make their own vitamin A.