题目

It’s hard to finish the work in a day. You’d better ____ your friends to help you.        A. call for      B. call on       C. call at D. call up 答案：B 解析: 略下列现象与分子热运动有关的是A．春天，百鸟争鸣B．夏天，波光粼粼C．秋天，丹桂飘香D．冬天，大雪纷飞