The skin, nails, brain, lining of the oral cavity, and the enamel of the teeth are formed from which layer?

a. Ectoderm
b. Endoderm
c. Mesoderm
d. Both a and b

a
RATIONALE: The skin, nails, brain, lining of the oral cavity, and the enamel of the teeth are formed from the ectoderm layer in the embryo phase of development.