题目

Oh, what a pity! It       so easy for me to bring those photographs I wanted to show you, but I’ve left them at home.   A. would have been         B. would be          C. had been           D. was   答案：A甲、乙两根保险丝均为同种材料制成，直径分别是d1＝0.5 mm和d2＝1 mm，熔断电流分别为2.0 A和6.0 A，把以上两根保险丝各取等长一段并联后再接入电路中，允许通过的最大电流是A．6.0 A B．7.5 A C．10.0 A D．8.0 A