Correct Answer: B

Rationale: The pinna, also known as the auricle, is the most visible part of the ear. It is responsible for capturing sound waves and directing them into the ear canal, where the process of hearing begins. The other structures mentioned, such as the cochlea, ear canal, and organ of Corti, play crucial roles in the auditory system but are not the most visible parts of the ear. The cochlea is a spiral-shaped cavity responsible for converting sound vibrations into neural signals. The ear canal is a tube that connects the outer ear to the eardrum. The organ of Corti is the actual sensory organ of hearing located in the cochlea.

Correct Answer: B

Rationale: The correct answer is B: 'To produce bile and detoxify substances.' The liver's primary functions include producing bile, which aids in the digestion and absorption of fats, and detoxifying harmful substances in the blood. While the liver does play a role in blood filtration, its key functions are related to bile production and detoxification. Choices C and D are incorrect because the liver does not produce insulin (produced by the pancreas) or red blood cells (produced in the bone marrow).

Correct Answer: A

Rationale: The correct answer is the cerebellum. The cerebellum, situated at the back of the brain, is responsible for coordinating voluntary movements and maintaining balance and posture. It receives information from the sensory systems, the spinal cord, and other parts of the brain to regulate motor movements. The cerebrum (choice B) is responsible for higher brain functions such as thinking and decision-making, the medulla oblongata (choice C) controls vital autonomic functions like breathing and heart rate, and the hypothalamus (choice D) is involved in regulating basic biological needs like hunger, thirst, and body temperature.

Correct Answer: B

Rationale: The correct answer is a ball and socket joint like the shoulder or hip joint, as it allows for movement in multiple directions, including rotation. This type of joint offers a high degree of mobility due to its structure, where the rounded end of one bone fits into the cup-like socket of another bone. A hinge joint (Choice A) allows movement primarily in one plane, like the elbow or knee. A pivot joint (Choice C) allows for rotation around an axis, seen in the neck joint. A saddle joint (Choice D) enables movements in multiple directions but to a lesser extent compared to a ball and socket joint, found in the thumb joint.

Correct Answer: B

Rationale: The thyroid gland is responsible for producing hormones, such as thyroxine, that play a crucial role in regulating metabolism, energy production, and overall growth and development in the body. The pituitary gland, while important for hormone regulation, does not primarily regulate metabolism. The adrenal gland is responsible for producing hormones like cortisol and adrenaline, which are more related to stress response than direct metabolism regulation. The pineal gland mainly produces melatonin, which regulates sleep-wake cycles and not metabolism. Therefore, the correct answer is the thyroid gland.