—How ______ you spell ring?
—R-I-N-G.[ ]
A. is
B. do
C. are
答案：B
The fireman started to put out the big fire_____ arriving at the burning building.
A．by
B．on
C．at
D．in
10kV验电笔的试验周期是（）
A.6个月
B.12个月
C.18个月
D.24个月
