Concept:A chicken egg has both protective accessory layers and the living part from which the embryo develops.
The germinal disc is the actual region of the egg cell, not an accessory covering.
Explanation:Accessory materials in a chicken egg are the extra protective and nutritive structures around the yolk.
Albumen is the egg white that cushions and feeds the embryo.
The shell membrane and the hard shell both protect the egg from injury and infection.
The germinal disc is a small white spot on the yolk surface where the female nucleus is located.
It is the part from which the embryo develops after fertilisation.
Therefore, it is not an accessory material but the actual egg cell region.
Answer:D. Germinal disc