In Developing Humans, the First Trimester Is a Time of Extreme

Multiple Choice

In developing humans, the first trimester is a time of extreme sensitivity to environmental risks, because

A) the placenta is most efficient at this time.
B) the embryo is very small at this time.
C) tissue differentiation is occurring at this time.
D) it is a period of dramatic growth.
E) the organ systems are maturing and particularly sensitive to disruption at this time.