Correct Answer: C

Rationale: During the second month of pregnancy, the heart of the developing fetus begins to develop separate chambers, forming the structure necessary for a fully functioning heart. This is a significant milestone in the prenatal development process. Choices A, B, and D are incorrect because the appearance of the umbilical cord as a primitive body stalk typically occurs around week 5-6, touch sensitivity extending to most of the body is more characteristic of the end of the second trimester, and the heartbeat is usually detectable through a stethoscope around the 18th to 20th week of pregnancy, not during the second month.

Correct Answer: C

Rationale: The best-known effect of smoking during the prenatal period is low birth weight. Smoking during pregnancy is a known teratogen that can lead to negative outcomes for the developing fetus, such as growth restrictions resulting in low birth weight. This condition can have significant long-term consequences on the child's health and development. Choices A, B, and D are incorrect as they are not the primary effect associated with smoking during the prenatal period. Colic is typically associated with digestive issues, respiratory distress at birth can be caused by various factors other than smoking, and delayed language development is not directly linked to smoking during pregnancy.

Correct Answer: B

Rationale: Brain weight increases tenfold from the twentieth week until birth. This rapid growth and development of the brain during the prenatal period is crucial for setting the foundation for future cognitive and neurological functions. Choices A, C, and D are incorrect because although they also undergo changes during prenatal development, none of them increase tenfold from the twentieth week until birth, unlike brain weight.

Correct Answer: B

Rationale: Dr. Dias's research findings indicate a correlation between the death of a spouse and a decline in the surviving partner's physical health. This correlation suggests a relationship between the two variables, but it does not necessarily imply a direct cause-and-effect relationship. Therefore, the correct conclusion supported by this study is option B - 'The death of a spouse is related to a decline in the surviving partner's physical health.' Option A is too direct in its causation claim, which is not proven by correlation alone. Option C reverses the cause and effect relationship suggested by the research. Option D introduces an unrelated third variable, which is not supported by the study's findings.

Correct Answer: B

Rationale: In the last weeks of pregnancy, most fetuses assume an upside-down position known as the head-down position or vertex presentation. This position is ideal for a smoother labor and delivery process as it helps the baby move through the birth canal. Fetal growth has already slowed down at this stage, so option C is incorrect. Option A is inaccurate as the fetus typically gains weight in the final weeks. Option D is incorrect because the fetus relies on the mother's immune system while in the womb.