题目

Hard work and lack of sleep have        her beauty and youth in recent years．     A. worn out      B.tried out         C made out      D．sent out 答案：A 解析: worn out耗尽，筋疲力尽；  tried out试验, 考验, 提炼；make out书写, 填写, 拼凑, 进展, 说明, 设法应付, 理解, 辨认出; sent out发出。把一个“8V2W”灯接在一个12V的电源上，为使灯正常发光，应串联一个    欧姆的电阻．