A-A+

(The first) electric lamp had two carbon rods

2022-08-01 21:46:05 问答库阅读 167 次

问题详情

(The first) electric lamp had two carbon rods (from which) vapor (served) to conduct the current (across) the gap.
A．The first
B．from which
C．served
D．across

参考答案

正确答案：B
解析：应将from which改为by which。