Correct Answer: B

Rationale: The left ventricle is the largest and strongest chamber of the heart. It pumps oxygenated blood to the body, making it vital for systemic circulation. The right atrium receives deoxygenated blood from the body, the right ventricle pumps this blood to the lungs, and the left atrium receives oxygenated blood from the lungs.

Correct Answer: B

Rationale: The skin serves several crucial functions in protecting the body. One of its primary roles is to act as a physical barrier against pathogens, preventing harmful microorganisms from entering the body. Choice A, 'To produce vitamin D,' is incorrect because while the skin is involved in vitamin D synthesis upon exposure to sunlight, its primary protective role is against pathogens. Choice C, 'To store nutrients,' is incorrect as the skin is not a primary organ for nutrient storage. Choice D, 'To regulate body temperature,' is a function of the skin, but the primary role in protecting the body is to act as a barrier against pathogens.

Correct Answer: C

Rationale: The correct answer is C: Skeletal muscle. Skeletal muscle is under voluntary control, allowing individuals to consciously regulate its contractions for movement. Examples of skeletal muscle control include actions like walking, running, and lifting weights. Smooth muscle (choice A) and cardiac muscle (choice B) are both involuntary muscles, meaning they are not under conscious control. While skeletal muscle is striated (choice D), striated muscle is a broader category that includes both voluntary (skeletal) and involuntary (cardiac) muscles.

Correct Answer: B

Rationale: The glomerulus is a key structure in the kidney responsible for filtering blood. It consists of a network of capillaries that filter waste products and excess substances from the blood, allowing the formation of urine. While the nephron, Bowman's capsule, and Loop of Henle are also essential components of the kidney's filtration system, the glomerulus is specifically involved in the initial blood filtration process. The nephron is the functional unit of the kidney, Bowman's capsule surrounds the glomerulus and collects the filtrate, and the Loop of Henle is responsible for reabsorption and concentration of urine, not the initial blood filtration.

Correct Answer: B

Rationale: Adrenaline, also known as epinephrine, is released by the adrenal glands during stress to prepare the body for rapid action. It helps in triggering the body's fight-or-flight response, increasing heart rate, and providing a burst of energy when faced with stressful situations. Insulin (Choice A) is produced by the pancreas to regulate blood sugar levels, not by the adrenal glands. Melatonin (Choice C) is a hormone that regulates sleep-wake cycles and is produced by the pineal gland, not the adrenal glands. Cortisol (Choice D) is another hormone produced by the adrenal glands, but it is not the primary hormone released during immediate stress responses; it is more involved in long-term stress regulation.