Correct Answer: A

Rationale: The word 'labile' is used to describe something that is constantly changing or easily altered. Therefore, the best synonym for 'labile' is 'extremely changing.' Choice B, 'suicidal,' is incorrect as it does not relate to the meaning of 'labile.' Choice C, 'rapidly changing,' is close but not as precise as 'extremely changing.' Choice D, 'with a high fever,' is completely unrelated to the meaning of 'labile.'

Correct Answer: A

Rationale: The word 'did' is correctly used in the sentence to form the past tense of the verb 'do.' In this context, 'did' is the appropriate term. The other words in the sentence, 'work,' 'asked,' and 'before,' are all used correctly and do not represent an incorrect word choice. Therefore, 'did' is the only word that is not used incorrectly in the given sentence.

Correct Answer: B

Rationale: The correct answer is B: 'Inducing sleep.' The term 'soporific' refers to something that causes sleepiness or drowsiness, leading to sleep. Choices A, C, and D are incorrect because they do not accurately represent the meaning of soporific. Choice A is the opposite since it means causing excitement, not drowsiness. Choices C and D are related to pain relief, which is not the primary association with the term soporific.

Correct Answer: B

Rationale: The correct answer is 'never shone' as the sentence is discussing a past event (Saturday). 'Never shone' is the correct past tense form to describe the sun not shining on a specific day in the past. Choices A, C, and D are incorrect because they do not provide the appropriate past tense form needed in this context. 'Never shines' is present tense, 'rarely shines' implies occasional shining, and 'sometimes shines' suggests occasional shining as well, none of which accurately convey the past event of the sun not shining on Saturday.

Correct Answer: B

Rationale: The correct answer is B: 'Purified.' Aseptic means free from contamination or sterile. While 'Sterilized' (choice A) is related to the elimination of all microorganisms, aseptic goes beyond sterilization to ensure freedom from contamination in a broader sense. 'Contaminated' (choice C) and 'Polluted' (choice D) are incorrect as they mean the opposite of aseptic, implying the presence of unwanted or harmful substances.