During the second trimester, a white, cheeselike substance called __________ emerges on the skin.

Correct Answer: C

Rationale: During the second trimester of pregnancy, a white, cheeselike substance called vernix emerges on the skin of the developing fetus. Vernix is a protective layer that helps prevent the skin from becoming waterlogged during the time in the amniotic fluid. Choice A, lanugo, is incorrect as lanugo refers to the fine, soft hair that covers the body of a fetus. Choice B, corpus luteum, is incorrect as it is a temporary endocrine structure involved in the menstrual cycle. Choice D, chorion, is incorrect as it is one of the membranes that surround the embryo and later the fetus.

Correct Answer: B

Rationale: The statement that the genetic makeup of the mother and the developing organism plays an important role in the harm done by teratogens is true. Genetic factors can influence susceptibility to teratogens, and the interaction between genetic and environmental factors plays a significant role in determining the impact on the developing fetus. This highlights the importance of considering both genetic and environmental influences when assessing risks to prenatal development. Choice A is incorrect as passive smoking can indeed be harmful to the developing fetus. Choice C is incorrect as the negative impact of teratogens is often not reversible. Choice D is incorrect as serious defects can occur throughout prenatal development, not just in the germinal period.

Correct Answer: D

Rationale: The difficulty in isolating the precise damage caused by illegal drugs during pregnancy is due to the fact that drug users often take several drugs, display other high-risk behaviors, and suffer from other stresses. This makes it challenging to identify the specific impact of each individual factor on prenatal development. Choices A, B, and C are incorrect because they do not address the complexity of the situation involving drug users during pregnancy. Most drug-using mothers refusing to participate in teratology research, the majority of babies not surviving, or drug-using mothers quitting during the first trimester do not directly explain the difficulty in isolating the precise damage caused by illegal drugs during pregnancy.

Correct Answer: A

Rationale: Terrance exhibits a combination of physical abnormalities like a thin upper lip, short eyelid openings, a small head, and a smooth philtrum, along with developmental delays and cognitive impairments. These characteristics are indicative of fetal alcohol syndrome (FAS), which is caused by maternal alcohol consumption during pregnancy. FAS is a severe condition resulting from prenatal alcohol exposure and is characterized by a range of physical, cognitive, and behavioral issues. Choice A, fetal alcohol syndrome, is the correct answer as it aligns with Terrance's symptoms and the effects of maternal alcohol consumption during pregnancy. Choices B, C, and D are incorrect because they do not encompass the full spectrum of symptoms and impairments presented by Terrance, which are specific to fetal alcohol syndrome.

Correct Answer: A

Rationale: Pregnant women are wise to avoid eating long-lived predatory fish, which are heavily contaminated with mercury. Mercury is a known teratogen, meaning it can negatively impact the development of the fetus and lead to birth defects. It is recommended that pregnant women choose fish with lower levels of mercury to reduce potential risks to the baby's health. Choices B, C, and D are incorrect because lead, polychlorinated biphenyls, and radiation are not typically found in fish at levels that pose significant risks to pregnant women and the developing fetus.