Correct Answer: A

Rationale: The correct answer is A. Hormone replacement therapy (HRT) is associated with an increased risk of cardiovascular events, such as heart attack and stroke, especially in patients with a history of coronary artery disease. Choice B is incorrect because HRT is actually known to decrease the risk of osteoporosis. Choice C is incorrect as HRT is associated with an increased risk of venous thromboembolism. Choice D is also incorrect as HRT may slightly increase the risk of breast cancer.

Correct Answer: C

Rationale: Estrogen is the correct answer. Amenorrhea, the absence of menstruation, is often due to hormonal imbalances. Estrogen plays a crucial role in regulating the menstrual cycle. Prescribing estrogen can help address these hormonal imbalances and restore menstrual cycles. Testosterone (Choice A) is not typically prescribed for amenorrhea in women as it can further disrupt hormonal balance. Follicle-stimulating hormone (Choice B) is involved in stimulating ovulation and follicle development, not the primary treatment for amenorrhea. Lactate (Choice D) is not a medication used to treat amenorrhea.

Correct Answer: B

Rationale: After exposure to a specific antigen, B cells undergo differentiation into plasma cells. Plasma cells are responsible for producing antibodies in response to the antigen. Choice A ('B cytotoxic cells') is incorrect because B cells do not differentiate into cytotoxic cells; cytotoxic cells are typically associated with T cells. Choice C ('Bursal cells') is incorrect as bursal cells are specific to birds and not relevant to human immune responses. Choice D ('Clonal equivalents') is incorrect as it does not describe the differentiation process of B cells exposed to antigens.

Correct Answer: D

Rationale: The correct answer is D, 'Increased glucose levels.' When the 'fight or flight' system is activated, the body releases glucose to provide energy for the impending response. This increase in glucose levels helps fuel the body's reaction to the perceived threat or stressor. Choices A, B, and C are incorrect because during the 'fight or flight' response, blood pressure, heart rate, and respiration rate typically increase to prepare the body to confront or flee from the perceived danger.

Correct Answer: B

Rationale: The correct answer is B: 'At the same time each day.' Hormonal contraceptives should be taken consistently at the same time each day to maintain stable hormone levels, which is crucial for their effectiveness. Taking them at random times can increase the risk of contraceptive failure. Choices A, C, and D are incorrect because taking hormonal contraceptives immediately after sexual intercourse, before going to bed at night, or on an empty stomach does not align with the recommended usage instructions for these drugs.