Correct Answer: C

Rationale: When people masticate, they use their gums and teeth to chew and physically break down food into smaller pieces for easier digestion. The process of mastication is essential for proper digestion in the human body. Choices A, B, and D are incorrect as fingers, eyes, ears, heels, and toes are not involved in the process of chewing or mastication.

Correct Answer: C

Rationale: The word 'impugn' means to challenge or attack the truth, integrity, validity, or honesty of something. It is not related to instilling (A), instructing (B), lamenting, or complaining (D). Impugn specifically involves questioning the accuracy or validity of a statement or argument, making choice C the correct answer.

Correct Answer: A

Rationale: A strident alarm is loud, harsh, and piercing. The word 'shrill' specifically denotes a high-pitched and piercing sound, which aligns well with the characteristics of a strident alarm. Therefore, 'shrill' is the most suitable answer in this context. Choices B, C, and D are incorrect because a strident alarm is not quiet (muted), unchanging (constant), or deep and full (resonant), but rather loud and harsh.

Correct Answer: C

Rationale: When someone is at the zenith of their career, it means they have reached the highest point or peak of success in their professional life. This suggests that they have achieved their utmost potential and are enjoying the height of their career accomplishments. Choice A, 'just getting started,' is incorrect as it implies the beginning of a career rather than the peak. Choice B, 'preparing for retirement,' is incorrect because being at the zenith of one's career usually signifies the prime of one's professional success, not the preparation for retirement. Choice D, 'having trouble with your superiors,' is incorrect as it is unrelated to the concept of reaching the peak of success in one's career.

Correct Answer: B

Rationale: The correct answer is B: Radius. The forearm consists of two long bones: the radius and the ulna. The radius is located on the thumb side of the forearm and is shorter than the ulna, which is on the pinky side. The humerus is the bone located in the upper arm, the scapula is the shoulder blade bone, and the fibula is a bone in the lower leg. Therefore, they are not the shorter bone in the forearm.