Correct Answer: C

Rationale: Out of millions of sperm released during ejaculation, only a small fraction, about 1 in 1,000, will approach the ovum. This statement is true as sperm face many obstacles and challenges on their journey to reach and fertilize an ovum. Choice A is incorrect because the average count of sperm in an ejaculate is typically in the millions, not billions. Choice B is incorrect as sperm do not find the ovum by following the current of fluid; they navigate using other mechanisms. Choice D is incorrect because while some sperm may move randomly in the vagina, the ones that approach the ovum do so through a more purposeful and directed movement.

Correct Answer: A

Rationale: To ensure adequate installation of the ophthalmic erythromycin 5% ointment in a newborn, the nurse should instill a thin ribbon into each lower conjunctival sac. This method helps to ensure proper distribution and effectiveness of the medication to prevent neonatal conjunctivitis. Choices B, C, and D are incorrect. Occluding the inner canthus after retracting the eyelids, mummy wrapping the infant, or stabilizing the instilling hand on the neonate's head are not appropriate actions for ensuring the proper installation of the ointment.

Correct Answer: A

Rationale: The correct answer is A: 'They regulate the development of traits.' Genes play a crucial role in regulating the development of traits by encoding proteins that control various bodily functions and characteristics. This process involves gene expression and the production of proteins that ultimately determine an individual's traits. Choice B is incorrect because genes do not have a direct role in preventing foreign particles from entering the body; this function is primarily carried out by the immune system. Choice C is incorrect as genes do not specifically work with lutein to influence development; genes operate independently to regulate trait expression. Choice D is incorrect as genes are not responsible for transferring oxygen in the bloodstream; this function is carried out by red blood cells and hemoglobin.

Correct Answer: D

Rationale: An amniocentesis in this scenario is most likely being performed to assess fetal lung maturity. This is necessary when considering early delivery due to macrosomia (large fetal size), which is a common concern in gestational diabetes. Evaluating fetal lung maturity is crucial to determine if the fetus's lungs are developed enough to support breathing independently outside the womb. The presence of a neural tube defect and chromosomal abnormalities are not typically assessed through amniocentesis in this situation, and determining the gender of the fetus is not the primary purpose of the procedure here.

Correct Answer: A

Rationale: Tay-Sachs disease is a genetic disorder that causes a progressive degeneration of the central nervous system, particularly in infants. Choice B, Cystic fibrosis, is a genetic disorder that primarily affects the lungs and digestive system, not the central nervous system. Choices C and D, Turner syndrome and Klinefelter syndrome, are chromosomal disorders that do not directly involve degeneration of the central nervous system.