The most rapid prenatal changes take place in the period of the __________.

Correct Answer: C

Rationale: The correct answer is C: embryo. The most rapid prenatal changes occur during the embryo stage, which spans from approximately 2 to 8 weeks after conception. This period is crucial as major organs and systems of the body develop rapidly, laying the foundation for future growth and development. The zygote stage is the initial single-celled entity formed by the union of sperm and egg, while the blastocyst stage involves the cluster of cells resulting from the zygote dividing and growing. The fetus stage follows the embryo stage and focuses on refining and growing existing structures rather than rapid development. Therefore, the embryo stage is where the most significant and rapid changes take place in prenatal development.

Correct Answer: D

Rationale: Lanugo helps the vernix stick to the skin. Vernix is a waxy substance that covers the fetus's skin during pregnancy. Lanugo is a fine, downy hair that helps to anchor the vernix to the skin, providing protection and nourishment to the developing fetus. Choices A, B, and C are incorrect as they do not accurately describe the role of lanugo in prenatal development.

Correct Answer: D

Rationale: In the eighth month of pregnancy, lanugo typically is shed. Lanugo is the fine, downy hair that covers a fetus's body to help regulate body temperature while in the womb. By the eighth month, many fetuses shed this hair as they prepare for birth. Choices A, B, and C are incorrect because fetal growth doubling, neuron production increasing, and the formation of eyes, ears, nose, jaw, and neck occur in earlier stages of pregnancy, not specifically in the eighth month.

Correct Answer: A

Rationale: In the germinal period of prenatal development, which lasts for about the first two weeks after fertilization, the developing organism is a zygote that has not yet implanted in the uterus. During this period, teratogens rarely have any impact because essential implantation and early cellular division processes are occurring. Teratogens are more likely to have significant effects during the later embryonic and fetal periods of development. Therefore, the correct answer is A. Choice B, embryonic period, is incorrect because teratogens have a higher likelihood of impacting development during this period. Choice C, fetal period, is also incorrect as teratogens can impact development during this stage as well. Choice D, prenatal, is a broad term encompassing the entire period of development from conception to birth and is not a specific developmental stage where teratogens have a minimal impact.

Correct Answer: A

Rationale: The correct answer is A: 'It is linked to impulsivity and overactivity.' Prenatal marijuana exposure has been associated with impulsivity and overactivity in children based on research findings. However, lasting consequences of prenatal marijuana exposure are not as well-established compared to other teratogens. Choice B is incorrect because lasting consequences are not firmly established. Choice C is incorrect because studies have shown negative effects of prenatal marijuana exposure. Choice D is incorrect as prenatal marijuana exposure is not primarily linked to physical malformations.