The embryo/fetus is most susceptible to damage from harmful environmental factors during
a. the first trimester
b. premature labor
c. toxoplasmosis
d. preeclampsia

Ans.

The embryo develops after 14 day of conception and till 8th week, it represents embryonic stage. The embryo is most susceptible to damage from external harmful factors, such as toxic chemicals, pathogens including viruses and bacteria, and poor nutrition in initial three months, which is known as critical period of differentiation.

Thus, the correct answer is 'option a). the first trimester.'

this is math not biology xd