题目

—Jim looks so sleepy that he keeps nodding his head in class.—Just as the saying goes， “____________.” It is bad for his health to stay up too late.A. Better late than neverB. Burn the candle at both endsC. No pains， no gains D. You are never too old to learn 答案：【答案】B【解析】试题分析：句意：吉姆看起来昏昏欲睡了，他在课堂上不断地打盹。——正如俗话所说，“劳累过度”，熬夜太晚对他的健康是不好的。A. Better late than never亡羊补牢；B. Burn the candle at both ends劳累过度；C. No pains， no gains不劳而获；D. You are never too old to learn活到老，学到老。结合上下某几何体的一条棱长为，在该几何体的正视图中，这条棱的投影是长为的线段，在该几何体的侧视图与俯视图中，这条棱的投影分别是长为a和b的线段，则a+b的最大值为（    ） A．                      B．               C．                         D．