Correct Answer: A

Rationale: An attenuated antigen used in a vaccine is alive but less infectious, aiming to stimulate an immune response. Choice B is incorrect because an attenuated antigen is not highly infectious. Choice C is incorrect as the antigen is intentionally altered to be less infectious. Choice D is incorrect as an attenuated antigen is not infectious.

Correct Answer: A

Rationale: During androgen therapy for hypogonadism, it is important to monitor liver function tests. Androgens can affect the liver, potentially leading to liver dysfunction. Monitoring liver function tests helps in early detection of any liver abnormalities. Kidney function tests (Choice B) are not typically affected by androgen therapy. Prostate-specific antigen (PSA) levels (Choice C) may be monitored for conditions like prostate cancer, but it is not directly related to androgen therapy for hypogonadism. A complete blood count (CBC) (Choice D) may not show specific changes related to androgen therapy for hypogonadism.

Correct Answer: A

Rationale: Antibodies are produced by B cells. B cells are specialized white blood cells that generate antibodies as part of the immune response. B cells differentiate into plasma cells that secrete antibodies. T cells play a role in cell-mediated immunity, not antibody production. Helper cells, or helper T cells, assist in activating B cells but do not directly produce antibodies. Memory cells store information about previous infections but do not actively produce antibodies.

Correct Answer: B

Rationale: The correct answer is B: Size. Muscular atrophy is characterized by a reduction in the size of muscle cells. This decrease in size can be due to various factors such as disuse, aging, or disease. Choice A, Number, is incorrect because muscular atrophy does not involve a decrease in the number of muscle cells but rather their size. Choice C, Vacuoles, is incorrect as vacuoles are not directly related to the definition of muscular atrophy. Choice D, Lipofuscin, is incorrect as lipofuscin is a pigment associated with aging and has no direct connection to the decrease in muscle cell size seen in muscular atrophy.

Correct Answer: A

Rationale: The correct answer is A. Hormone replacement therapy (HRT) is associated with an increased risk of cardiovascular events, including heart attack and stroke, especially in patients with a history of cardiovascular disease. Choice B is incorrect because HRT does not decrease the risk of osteoporosis; in fact, it may increase the risk of certain conditions like venous thromboembolism, as mentioned in choice C. Choice D is also incorrect as HRT has been associated with a slight increase in the risk of breast cancer.