Pls pl hel need it now

A developing human embryo produces a special type of hemoglobin that is not found in the blood of an infant, child, or adult.
Which statement best explains how this can be?

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.

c) An embryo and an adult have different genes for hemoglobin. Hope this helps!

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.