Teratogens: select one:

a. are environmental agents that can harm the embryo or fetus.

b. are most damaging during the fetal period of development.

c. are only those substances the mother's body produces.

d. harm the fetus only when taken in extremely large doses.

The answer is A. Teratogens are substances that impair the proper development of embryo or fetus. They include drugs, infections, radiation, and chemicals. The agents could cause the fetus to be physically or mentally impaired. Children born having been exposed to teratogens that affect their brain development could exhibit reduced IQ, communication challenges, and etcetera.

Teratogens: a. are environmental agents that can harm the embryo or fetus.

Teratogens may cause a birth defect in the child.

The classes of teratogens include radiation, maternal infections, chemicals and drugs (heroin and cocaine). About 7% of all congenital disorders are caused by teratogens.