Correct Answer: C

Rationale: During the last half of the first month of pregnancy, the nervous system develops the fastest among the options provided. This rapid development of the nervous system is crucial for the overall growth and functioning of the fetus. The nervous system includes the brain and spinal cord, which are essential for various bodily functions and will continue to develop throughout the pregnancy. The circulatory system, although important, does not develop at the fastest rate during this stage. The endocrine system and skin also play significant roles in the development of the fetus but are not the systems that develop the fastest in the last half of the first month of pregnancy.

Correct Answer: B

Rationale: The correct answer is B: 'In South Africa, 30 percent of all pregnant women are HIV-positive.' This statement is true as South Africa has a high prevalence of HIV among pregnant women, emphasizing the need for interventions to prevent mother-to-child transmission. Choices A, C, and D are incorrect. Choice A is inaccurate as women account for more than 50% of new HIV infections globally. Choice C is misleading as the majority of new HIV infections actually occur in sub-Saharan Africa, not just developing countries. Choice D is also incorrect as without treatment, the risk of mother-to-child transmission is higher than 30%.

Correct Answer: A

Rationale: Newborn infants who are brain damaged or who have experienced birth trauma often display disturbed REM-NREM sleep cycles. This disruption in the sleep cycle can be a sign of neurological issues and can impact the newborn's overall health and development. Choice B is incorrect because infants with brain damage or birth trauma may actually cry more due to their discomfort or neurological issues. Choice C is incorrect because spending about 20 percent of total sleep time in REM sleep is not necessarily specific to brain-damaged or birth-traumatized infants. Choice D is incorrect because having very low or inaudible cries is not a common characteristic associated with brain damage or birth trauma in infants.

Correct Answer: D

Rationale: Dr. Anderson should use an experimental design to determine the cause-and-effect relationship between domestic violence and anger in children. In an experimental design, the researcher manipulates the independent variable (in this case, exposure to domestic violence) to observe its effect on the dependent variable (anger in children). This design allows for the establishment of a cause-and-effect relationship by controlling for other variables that may influence the outcomes. Observational design (Choice B) involves observing subjects in their natural environment without interference, correlational design (Choice C) examines the relationship between variables without manipulating them, and structured design (Choice A) typically refers to a study with predetermined procedures and data collection methods, which may not be suitable for establishing cause-and-effect relationships.

Correct Answer: B

Rationale: The correct answer is the third month of pregnancy (choice B). During the third month of pregnancy, which is around 9-12 weeks, a fetal heartbeat can typically be heard using a stethoscope. This is an exciting milestone for expectant parents as it provides reassurance about the baby's well-being. Choices A, C, and D are incorrect because by the fourth week of pregnancy, the fetal heartbeat is not usually detectable with a stethoscope. The end of the second trimester and the beginning of the third trimester are too late in the pregnancy timeline for this milestone.