题目

— Did Jack come back early last night? — Yes. It was not yet eight o’clock ______ he got home. A. before            B. when              C. that                 D. until 答案：B如图所示的电路，当电路闭合后，电流表A1的示数如图所示，A2的示数如图所示．（1）请写出流过电灯L2的电流和干路中电流大小，并说明判断依据．（2）求：流过电灯L1的电流大小．