By the end of Greta's first month of pregnancy, her embryo __________.

Correct Answer: B

Rationale: By the end of Greta's first month of pregnancy, her embryo is about ¼ inch long. During the first month of pregnancy, the embryo is in the very early stages of development, and its size is typically around ¼ inch as it continues to grow and develop in the uterus. Choices A, C, and D are incorrect because sensory abilities like sensing the world, sucking thumb, and curling toes develop later in the pregnancy as the embryo progresses through different stages of 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.

Correct Answer: A

Rationale: Recent evidence suggests that paternal alcohol use around the time of conception can alter gene expression. This means that paternal alcohol consumption can potentially impact the genes and genetic materials passed on to offspring, affecting their development and health. Choice B is incorrect because fetal alcohol syndrome is typically associated with maternal alcohol consumption during pregnancy, not paternal alcohol use around conception. Choice C is incorrect as there is no direct link between paternal alcohol use and blood vessel abnormalities. Choice D is incorrect as paternal alcohol use can indeed have negative effects on the developing organism, particularly through altering gene expression.