In Human Development, an Embryo Is Most Sensitive to Chemicals

Multiple Choice

In human development, an embryo is most sensitive to chemicals, radiation or pathogens at first trimester, because this is the time that

A) organ systems are growing in size.
B) cells are rapidly dividing and tissues are differentiating.
C) the enlarged yolk pushes the gastrula into a disk shape.
D) the allontoic stalk is disconnected from the placenta.
E) All of the above