Correct Answer: C

Rationale: The correct answer is C: Humerus and scapula. The rotator cuff is a group of muscles and tendons that help stabilize the shoulder joint. Specifically, the rotator cuff muscles help to stabilize the head of the humerus (the upper arm bone) within the shallow socket of the scapula (shoulder blade). This stabilizing action is crucial for maintaining shoulder joint function and preventing injuries.

Choices A, B, and D are incorrect because the rotator cuff primarily stabilizes the humerus and scapula, not the radius, ulna, or clavicle.

Correct Answer: C

Rationale:
Tofu is a plant-based source of protein that can provide a significant amount of protein to a person on a vegan diet. It is made from soybeans and is a versatile ingredient that can be used in various dishes to increase protein intake.
Tofu is a good option for vegans looking to meet their protein needs. Eggs and fish are not suitable for a vegan diet as they are animal products. While leafy greens do contain some protein, they are not considered a significant protein source compared to tofu.

Correct Answer: C

Rationale: The correct answer is C: 26. The human foot consists of 26 bones, including tarsal bones, metatarsal bones, and phalanges. These bones collaborate to offer support, flexibility, and stability for various activities like standing, walking, and running.
Choice A (6) is incorrect as it is too low for the number of bones in the human foot.
Choice B (16) is incorrect as it underestimates the actual number of bones in the foot.
Choice D (36) is incorrect as it overestimates the number of bones in the human foot.

Correct Answer: A

Rationale: The anterior chamber of the eye is the fluid-filled space located between the cornea and the iris in the front part of the eye. It contains aqueous humor and helps maintain intraocular pressure. The space between the iris and the lens is known as the anterior chamber, making option A, 'iris and lens,' the correct choice. Options B, C, and D are incorrect because they do not describe the correct anatomical location of the anterior chamber.

Correct Answer: A

Rationale: Gallstones become most problematic when they block a duct, such as the bile duct or cystic duct. This blockage can lead to various complications, including inflammation, infection, and even damage to the gallbladder or liver. In severe cases, a blocked duct can cause intense pain, jaundice, and other serious symptoms that require medical intervention.

Choices B, C, and D are incorrect because the presence of cholesterol or bilirubin in gallstones or the process of dissolution do not necessarily indicate when gallstones become most problematic. The critical issue arises when the stones obstruct a duct, leading to complications.