The MOST sensitive or critical period of prenatal development is:

This means that babies may have a higher chance for major heart defects if their mothers’ take this medication during the heart’s critical period of development. We know that the heart’s critical period of development is from 3 to 6 embryonic weeks (5 to 8 gestational weeks).

b brown mice / white sand dunes

sex cells are usually half's then they find another half and make a fertilize egg