Correct Answer: A

Rationale: The correct answer is A: 'To voluntarily refrain from something.' Abstain means to choose not to do or have something, especially something you like or enjoy. Choices B, C, and D are incorrect because abstain does not mean to consume something, to eat, or to encourage. It specifically refers to the act of voluntarily refraining from an action or practice.

Correct Answer: A

Rationale: The correct answer is A: 'She had one goal: to win the race.' This sentence uses a colon to introduce the purpose or explanation that follows. It is a grammatically correct use of a colon. Choice B is incorrect as the colon is not needed after 'needs'; a list of items follows, which does not require a colon. Choice C is a simple statement of time and does not require a colon. Choice D is also incorrect since a colon is not suitable after 'bought'; the items bought are listed without the need for a colon.

Correct Answer: B

Rationale: The correct answer is B, 'Vague.' Nebulous means something that is vague or unclear. Choice A, 'Clear,' is incorrect as it represents the opposite meaning of nebulous. Choice C, 'Precise,' is incorrect as it denotes clarity and exactness, which is the opposite of nebulous. Choice D, 'Obvious,' is also incorrect as it implies something that is easily understood or seen, unlike nebulous which refers to something unclear or hazy.

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Rationale: If a theory is considered obsolete, it means that it is outdated and no longer in current use or practice.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 Choice C, 'Useful,' is incorrect because an obsolete theory is no longer considered useful due to being outdated.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.