增量式光电编码器的测量精度取决于它所能分辨的最小角度，而这与码盘圆周上的狭缝条纹数n有关
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She wondered what over here.
A. has happened
B. was happened
C. had been happened
D. had happened
The fire of London on the right of September, 1666.
A. was broken out
B. had broken out
C. broke out
D. broken out
How long the concert ?
A. has; been lasted
B. did; last
C. will; be lasted
D. was; lasted
we to be careful of rats since the whole street was full of rubbish.
A. warned
B. have warned
C. have been warned
D. were warning
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