Which hormone stimulates the production of red blood cells?

Correct Answer: B

Rationale: Erythropoietin is the correct answer. It is the hormone responsible for stimulating the production of red blood cells. Erythropoietin is produced by the kidneys in response to low oxygen levels in the blood. This hormone promotes the generation of more red blood cells to increase the blood's oxygen-carrying capacity. Insulin (Choice A), Glucagon (Choice C), and Thyroxine (Choice D) do not stimulate the production of red blood cells. Insulin regulates blood sugar levels, Glucagon increases blood sugar levels, and Thyroxine regulates metabolism.

Correct Answer: C

Rationale: The thyroid gland is responsible for regulating metabolism. It produces hormones such as thyroxine, which plays a key role in influencing the body's metabolic rate. The pituitary gland is known as the 'master gland' but is not directly responsible for regulating metabolism. The adrenal gland is involved in the stress response and producing hormones like cortisol, not primarily regulating metabolism. The pineal gland produces melatonin, which regulates sleep-wake cycles, not metabolism. Therefore, the correct answer is the thyroid gland.

Correct Answer: B

Rationale: Vitamin C is essential for the synthesis of collagen, a crucial protein that plays a significant role in maintaining the structural integrity of skin, blood vessels, and bones. Collagen is responsible for the strength, elasticity, and firmness of these tissues. Without sufficient vitamin C, the body cannot form collagen properly, leading to various health issues like scurvy, impaired wound healing, and fragile blood vessels. Choices A, C, and D are incorrect. Vitamin A plays a role in vision, immune function, and skin health. Vitamin D is crucial for bone health and immune function, while Vitamin E is an antioxidant that helps protect cells from damage.

Correct Answer: B

Rationale: The pineal gland secretes melatonin, a hormone that plays a crucial role in regulating the sleep-wake cycle. Melatonin production is influenced by exposure to light, with levels increasing in the evening to promote sleep and decreasing in the morning to signal wakefulness. Choices A, C, and D are incorrect because the thyroid gland primarily regulates metabolism, the adrenal gland produces hormones like adrenaline and cortisol related to stress response, and the pituitary gland controls various functions by releasing different hormones but not specifically related to regulating sleep.

Correct Answer: A

Rationale: Insulin is the hormone that regulates blood sugar levels by promoting the uptake of glucose into cells. It is produced by the pancreas and helps to lower blood sugar levels when they are too high. Glucagon, on the other hand, works in opposition to insulin by raising blood sugar levels when they are too low. Cortisol and thyroxine play different roles in the body and are not primarily responsible for regulating blood sugar levels.