The galvanometer indicated______. A．that Henry's assistant had connected the wire B．that Henry had been able to produce a voltage C．zero constantly D．the iron bar had been placed across the poles of the electromagnet
A. A．that B.that C.zero D.the
【参考答案】
B 解析：本题是一道具体细节题。问电流计指示了什么。利用查阅式阅读法，文章第三段后半部分指出，亨利着手搞起了磁、......