The correct option is C Aleurone layer
The layer of the endosperm of maize rich in protein is the aleurone layer. Outer covering of the endosperm separates the embryo by a proteinous layer called aleurone layer in monocots.
A sheath called coleoptile and coleorhiza encloses the plumule and radicle of the maize seed, respectively. This is a characteristic of monocots.