Correct Answer: C

Rationale: The term 'captivated' in the sentence indicates that the audience was completely engrossed and engaged by the speaker's compelling story. This implies that they were absorbed and highly interested in what was being presented. Choices A, B, and D are incorrect because 'captivated' suggests a positive and attentive reaction from the audience rather than boredom, confusion, or disagreement.

Correct Answer: C

Rationale: The correct answer is 'Idyllic' because it accurately captures the peaceful and picturesque nature of the setting. The image of a lone cabin nestled among towering pines with smoke curling from its chimney into the crisp mountain air evokes a sense of tranquility and beauty. 'Bland' (choice A) is incorrect as it suggests something dull or uninteresting, which does not align with the vivid imagery described. 'Urban' (choice B) is also incorrect as it refers to a city or town setting, which is the opposite of the isolated cabin in the mountains. 'Sterile' (choice D) is incorrect as it conveys a lack of warmth and character, which is not reflective of the cozy and inviting atmosphere portrayed in the description.

Correct Answer: A

Rationale: Option A correctly uses the past perfect tense to show an action that was completed before another past action. In this sentence, 'the party had already begun' indicates that the party started before 'I arrived.' This structure is typical of the past perfect tense. Choice B uses the past perfect tense but does not demonstrate the sequence of actions in the past. Choice C uses the future perfect tense, indicating completion of an action by a future time. Choice D uses the past perfect continuous tense, not the simple past perfect tense required by the question.

Correct Answer: B

Rationale: The past tense of the verb 'discover' is 'discovered.' In this case, the scientist already found a new species of butterfly, indicating a past action. 'Discovered' is the correct past tense form of 'discover.' The other options do not represent the past tense form of the verb. 'Discovers' is present tense, 'discovering' is present participle, and 'discovery' is a noun, not a verb tense.

Correct Answer: A

Rationale: Option A correctly uses the passive voice by placing the emphasis on the object (letter) that received the action (was written) rather than the subject performing the action. The phrase 'by Mary' indicates the agent who performed the action, making it a clear example of the passive voice structure. Choices B, C, and D are all in the active voice, where the subject performs the action directly on the object. In the context of identifying the correct usage of the passive voice, option A stands out as the only suitable example.