Down Syndrome is the most common serious birth defect afflicting child

QUESTION-1. The correct answer is (b). Trisomy 21 is a specific condition where there are three 21st chromosomes. This condition is named Down Syndrome.
Choice (a) is incorrect because aneuploidy is the general term for an abnormal number of chromosomes. While Trisomy 21 is one type of aneuploidy, there can be others.
Choice (c) is incorrect because the passage states that Trisomy 21 is the most common form of mental retardation, not the only cause.
Choice (d) is incorrect because sexual underdevelopment can be caused by many conditions, not just Trisomy 21.

QUESTION-2. The correct answer is (d). The passage tells us that as women age they have a greater likelihood of carrying a child with Down Syndrome. If today's couples are postponing childbirth, then it could explain why today's couples see a higher incidence of Down Syndrome offspring.
Choice (a) is incorrect because if the population growth is decreasing, there should be fewer incidents of Down Syndrome.
Choice (b) is incorrect because the passage contains no information concerning a link between drug abuse and Down Syndrome.
Choice (c) is incorrect because people with Down Syndrome have a very small chance of reproducing successfully. So, while this answer could produce a small increase in Down syndrome, the actual number of cases would be statistically very low and would not likely lead to the conclusion that Down Syndrome has been steadily increasing in the last 10 years.
Choice (e) may be true, but nothing in the passage suggests that it would lead to a higher likelihood of babies with Down Syndrome.

QUESTION-3. The correct answer is (c). The passage says that those afflicted with Down Syndrome may be sexually underdeveloped, which could certainly contribute to the inability to conceive but may not necessarily impact the physical ability to engage in sexual intercourse.