题目

一节干电池电压为伏。马德堡半球实验证明存在，且很大。首先发现电流周围存在磁场的物理学家是。 答案：【1】1.5【2】大气压【3】奥斯特 Having finished their morning work, the clerks stood up behind their desks, ________ themselves. A. expanding B. extending C. expressing D. stretching