When a human embryo develops, it produces a special type of hemoglobin not found in infant, child, or adult blood. Which statement best explains how an embryo can produce a different type of hemoglobin from that of an infant, a child, or an adult?

A.) Humans have genes for different types of hemoglobin, and they are expressed at different times.

B.) Human genes change slowly as a person ages.

C.) An embryo and an adult have different genes for hemoglobin.

D.) As the embryo develops and cells differentiate, certain genes are lost.