Correct Answer: B

Rationale: If a theory is considered obsolete, it means that it is outdated and no longer in current use or practice. Choice A, 'Advanced,' is incorrect as it implies progression rather than obsolescence. Choice C, 'Useful,' is incorrect because an obsolete theory is no longer considered useful due to being outdated. Choice D, 'Innovative,' is incorrect as it suggests newness and originality, which are opposite to being obsolete.

Correct Answer: B

Rationale: The correct answer is B, 'Emetic.' An emetic is a medication specifically designed to induce vomiting. This helps the body expel toxic substances or clear the stomach. Choice A, 'Laxative,' aids in relieving constipation by promoting bowel movements, not inducing vomiting. Choice C, 'Vaccine,' is a substance used to stimulate the immune system against specific diseases, not to induce vomiting. Choice D, 'Analgesic,' refers to a medication used to relieve pain, not to induce vomiting. Therefore, options A, C, and D are incorrect in the context of inducing vomiting.

Correct Answer: D

Rationale: The term 'insidious' typically describes something that occurs gradually and subtly, often without being noticed until it has become more serious or established. Therefore, the development of the disease being insidious suggests that it was gradual, aligning best with the meaning of the word in this context. Choice A, 'momentous,' means significant or important, which is opposite in meaning to insidious. Choice B, 'sudden,' indicates something happening quickly and unexpectedly, contrary to the gradual nature of an insidious development. Choice C, 'innocuous,' means harmless or not likely to cause harm, which does not accurately reflect the negative and harmful connotation associated with an insidious disease development.

Correct Answer: B

Rationale: The correct answer is B: 'Straightforward.' Guileless means innocent, sincere, and without deceit. It describes someone who is honest and straightforward in their actions and speech. Choices A, C, and D are incorrect. 'Deceptive' means misleading or dishonest, 'Complex' means having many intricate parts, and 'Untrustworthy' means not reliable or trustworthy, all of which are opposite in meaning to guileless.

Correct Answer: B

Rationale: The correct answer is B: 'Exhausted.' Lethargic describes a state of feeling sluggish, tired, and lacking energy, which aligns with being exhausted. Choice A, 'Energetic,' is the opposite of lethargic and does not fit the description. Choice C, 'Confused,' refers to a state of disorientation rather than physical tiredness. Choice D, 'Restless,' implies a state of agitation or inability to relax, which contrasts with the typical presentation of someone who is lethargic.