Correct Answer: A

Rationale: Chromosomes are rod-shaped structures that carry genetic information in the form of DNA. They are typically seen as elongated structures when visualized under a microscope. Choice B, circular, is incorrect as chromosomes do not have a circular shape; they are linear. Choice C, cone-shaped, is not accurate as chromosomes do not resemble cones in any way. Choice D, octagonal, is also incorrect as chromosomes do not have an octagonal appearance. Therefore, the correct answer is A, rod-shaped, which accurately describes the shape of chromosomes.

Correct Answer: C

Rationale: The correct answer is C. The development of arms and legs occurs during the critical period of the fourth to eighth weeks of pregnancy. This timeframe is crucial for the formation of limbs and other key body parts. Choices A, B, and D are incorrect because the development of the lungs, heart, and stomach respectively occurs at different stages of fetal development and is not primarily associated with the fourth to eighth weeks of pregnancy.

Correct Answer: A

Rationale: The correct answer is A: A pattern of fetal late decelerations. Late decelerations during a contraction stress test are concerning as they indicate uteroplacental insufficiency, which can pose a risk to fetal well-being. Reporting this finding to the healthcare provider is crucial for prompt intervention. Choice B, fetal heart rate accelerations with fetal movement, is a reassuring sign of fetal well-being and does not raise immediate concerns. Choice C, absence of uterine contractions within 20 minutes, may require further assessment but is not as critical as late decelerations. Choice D, spontaneous rupture of membranes, is important but not the most immediate concern during a contraction stress test.

Correct Answer: A

Rationale: The correct characteristic of supermales, individuals with an XYY chromosome pattern, is that they are somewhat taller than average. Choice B is incorrect as supermales do not exhibit minimal facial hair growth compared to normal males. Choice C is incorrect as gynecomastia, the development of male breasts, is not a characteristic of supermales. Choice D is also incorrect as impotence is not a typical characteristic associated with supermales.

Correct Answer: B

Rationale: The correct answer is B. According to the study by Fellman in 2013, the chances of having twins actually increase with parental age. Choice A is incorrect as the study does not specify a younger age for conceiving to increase the chances of twins. Choice C is incorrect as the frequency of intercourse before conception is not a highlighted factor in the study. Choice D is also incorrect as the study does not discuss the impact of fertility drugs on the likelihood of having twins.