Correct Answer: D

Rationale: When children exhibit traits that are more similar to their biological parents than their adoptive parents, it indicates a strong genetic influence on those traits. This similarity suggests that genetics play a significant role in the development of the observed characteristics. Choice A is incorrect because genetic characteristics do not change over time in this context. Choice B is incorrect as it implies that heredity is the only factor, disregarding the impact of the environment. Choice C is also incorrect as it suggests that only the environment influences trait development, overlooking the genetic contribution.

Correct Answer: C

Rationale: Down's syndrome, also known as trisomy 21, is caused by the presence of an extra chromosome on the 21st pair. Choice A is incorrect as alcohol abuse is not the cause of Down's syndrome. Choice B is incorrect because Down's syndrome is not related to sex-linked chromosomal abnormalities. Choice D is also incorrect as drug abuse by the mother during pregnancy is not the cause of Down's syndrome.

Correct Answer: A

Rationale: During the first stage of labor, effective uterine contractions lead to cervical dilation. Dilation of the cervix is a key indicator that uterine contractions are progressing labor. Descent of the fetus to -2 station (Choice B) is related to the fetal position in the pelvis and not a direct indicator of uterine contraction effectiveness. Rupture of the amniotic membranes (Choice C) signifies the rupture of the fluid-filled sac surrounding the fetus and does not directly reflect uterine contraction effectiveness. An increase in bloody show (Choice D) can be a sign of impending labor, but it is not a direct indicator of uterine contraction effectiveness.

Correct Answer: C

Rationale: Individuals with Klinefelter syndrome have an extra X chromosome (XXY) and typically have reduced testosterone levels, which can lead to gynecomastia (enlarged breasts). This condition is not usually associated with Down syndrome (choice A), XYY syndrome (choice B), or Turner syndrome (choice D), making them less likely to have gynecomastia.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Advanced parental age, particularly maternal age, is associated with an increased risk of Down's syndrome in offspring. As parents get older, the likelihood of having a child with Down's syndrome increases. Choices B, C, and D are incorrect because the risk of Down's syndrome is known to rise with parental age, especially maternal age, due to the increased likelihood of chromosomal abnormalities during egg formation.