Question

【题目】He seldom stays up late at night, necessary, to keep himself full of energy the next day.

A. if B. unless C. since D. though

Answer 1

【答案】B

【解析】

试题分析：句意：除非有必要，否则为了第二 天能精力充沛，他很少熬夜很晚。if意为 “如果”；until意为“直到”；though意为 “虽然”。unless意 为“除非”，相当于if not ,符合句意。故选B。