Correct Answer: B

Rationale: The gallbladder's main function is to store and concentrate bile produced by the liver. Bile is essential for the digestion and absorption of fats in the small intestine. Therefore, the correct answer is B, as the gallbladder acts as a reservoir for bile rather than producing it. Choices A, C, and D are incorrect because the gallbladder does not produce bile, detoxify harmful substances, or regulate blood sugar in the digestive system.

Correct Answer: B

Rationale: The correct answer is B: Support and protection. The primary functions of the skeletal system include providing structural support to the body and protecting internal organs. While the skeletal system also plays a role in hematopoiesis (production of blood cells) and stores minerals, its main function is to support the body's framework and protect vital organs. Choices A, C, and D are incorrect as they do not directly relate to the primary functions of the skeletal system.

Correct Answer: B

Rationale: The correct answer is B, Skeletal muscle. Skeletal muscle is a type of voluntary muscle tissue, allowing conscious control over its movement. Unlike smooth and cardiac muscle, which are involuntary, skeletal muscle is under direct voluntary control. Cardiac muscle (choice A) is involuntary and found in the heart. Smooth muscle (choice C) is also involuntary and found in the walls of internal organs. While skeletal muscle is striated (contains stripes), choice D is not the best answer as it does not specifically address the voluntary nature of skeletal muscle.

Correct Answer: C

Rationale: The correct answer is the front portion of the parietal lobe. The motor cortex, located in this area, is responsible for planning, controlling, and executing voluntary movements. It plays a crucial role in coordinating the body's movement. Choice A, the top, middle portion of the parietal lobe, is incorrect as this region is more involved in processing sensory information rather than controlling movement. Choice B, the back of the head, is incorrect as it typically refers to the occipital lobe responsible for processing visual information. Choice D, around the auditory cortex, is incorrect as the auditory cortex is primarily involved in processing auditory information, not controlling body movement.

Correct Answer: A

Rationale: Insulin is secreted by the pancreas to lower blood glucose levels by facilitating the uptake of glucose into cells. It promotes the storage of glucose as glycogen in the liver and muscles, reducing blood sugar levels. Glucagon, on the other hand, works to raise blood glucose levels by stimulating the breakdown of glycogen into glucose and releasing it into the bloodstream. Somatostatin regulates the endocrine system and inhibits the release of insulin and glucagon. Cortisol is a hormone produced by the adrenal glands, not the pancreas, and it plays a role in stress response and metabolism, but it does not directly lower blood glucose levels.