Correct Answer: B

Rationale: The correct answer is B: Elbow joint. A hinge joint allows movement primarily in one plane, enabling bending and straightening actions. The elbow joint specifically functions as a hinge joint, facilitating the bending and straightening of the arm. The other options, such as the hip joint (A), shoulder joint (C), and knee joint (D), are not examples of hinge joints as they allow movement in multiple planes with more complex motions.

Correct Answer: B

Rationale: The correct answer is the Retina. The retina in the eye contains specialized cells called photoreceptors that detect light and convert it into neural signals. These signals are then transmitted to the brain via the optic nerve for visual processing. The iris is responsible for controlling the amount of light entering the eye by adjusting the size of the pupil, while the lens helps focus light onto the retina. The pupil is simply the opening in the center of the iris that allows light to enter the eye.

Correct Answer: D

Rationale: The primary function of the liver related to digestion is to filter and detoxify byproducts of digestion, including toxins and metabolic waste products. While the liver does produce bile and convert waste ammonia into urea, these functions are not directly related to digestion. Storing bile is mainly done by the gallbladder, not the liver.

Correct Answer: C

Rationale: The correct answer is Iron (II) (Fe2+), which is the cation found at the center of a heme group. Heme contains an iron (II) ion that is coordinated within the porphyrin ring structure. This iron ion is crucial for the function of heme in binding and transporting oxygen in hemoglobin and myoglobin. Choice A (Cr (III)) is incorrect as chromium is not typically found at the center of a heme group. Choice B (Cu (II)) is incorrect as copper is not the cation typically present in heme. Choice D (Iron (III)) is also incorrect as heme predominantly contains iron (II) at its center, not iron (III).

Correct Answer: B

Rationale: Lacteals are lymphatic capillaries in the small intestine that specialize in absorbing dietary lipids. These lipids are then transported into the lymphatic system for further processing and distribution throughout the body. Choice A (Carbohydrates) is incorrect because carbohydrates are primarily digested and absorbed in the small intestine by enzymes and transported to the liver. Choice C (Proteins) is incorrect because proteins are broken down into amino acids and absorbed in the small intestine, mainly by the villi. Choice D (Nonpolar nutrients) is incorrect as it is a vague term and not specific to what lacteals absorb, which are primarily lipids.