Correct Answer: C

Rationale: The correct answer is C. The primary immune response is slower and less powerful compared to the secondary immune response. During the primary response, immune cells encounter the antigen for the first time, necessitating the activation and proliferation of specific immune cells. In contrast, the secondary response benefits from memory cells that quickly recognize the antigen, enabling a faster and more potent immune response. Choices A, B, and D are incorrect. While macrophages play a role in presenting antigens to T cells, this is not a defining difference between primary and secondary responses. Humoral immunity involves B lymphocytes in both primary and secondary responses, so it does not differentiate the two. Suppressor T cells primarily function to regulate the immune response but are not a key factor distinguishing primary from secondary responses.

Correct Answer: B

Rationale: Adrenaline, also known as epinephrine, is produced by the adrenal glands in response to stress. It helps prepare the body for the 'fight or flight' response by increasing heart rate, dilating airways, and mobilizing energy sources. Choice A, Insulin, is incorrect as it is produced by the pancreas and regulates blood sugar levels. Choice C, Glucagon, is also produced by the pancreas and functions to increase blood glucose levels. Choice D, Thyroxine, is produced by the thyroid gland and regulates metabolism, not specifically in response to stress.

Correct Answer: B

Rationale: Bile is a digestive fluid produced in the liver, stored in the gallbladder, and it aids in the digestion of fats by emulsifying them. Emulsification helps to break down fats into smaller particles, facilitating their digestion by enzymes in the small intestine. Choice A is incorrect because bile is not produced in the pancreas, and it is not stored in the liver. Choice C is incorrect as bile is not produced in the stomach, and it does not neutralize acid. Choice D is also incorrect as bile is not produced in the gallbladder, and its primary function is not to break down proteins.

Correct Answer: D

Rationale: During inspiration, the diaphragm contracts and moves downward. This action increases the volume of the thoracic cavity, which lowers the air pressure inside the lungs, allowing air to flow in. The downward movement and contraction of the diaphragm create the necessary space for the lungs to expand and fill with air. Choice A, 'It moves upward,' is incorrect as the diaphragm moves downward. Choice B, 'It moves downward,' is partially correct but misses the contraction aspect. Choice C, 'It expands,' is incorrect as the diaphragm itself does not expand during inspiration. Therefore, choice D, 'It contracts and moves downward,' is the most accurate description of the diaphragm's action during inspiration.

Correct Answer: A

Rationale: The correct answer is 'Superior.' 'Superior' refers to a position toward the head, while 'inferior' is the term for a position toward the feet. In the given example, the hand belongs to the superior extremity, which includes structures closer to the head. 'Inferior' is incorrect as it refers to a position away from the head or toward the feet. 'Medial' describes a position closer to the midline of the body, while 'lateral' refers to a position farther away from the midline.