合像水平仪采用了光学放大,并以()来提高对准精度,可使水准器玻璃管的曲率减小。因此,测量时气泡达到稳定的时间短。
A.单像重合
B.双像重合
C.多像
参考答案:B
I don't think he could have finished his work last night, ________? [ ]
A. do I
B. did he
C. has he
D. could he
罗茨鼓风机可以通过出口闸阀控制曝气量。