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【单选题】
注塑机每工作（）小时须更换一次压力油，更换压力油时不可将新旧油混合使用，同时应拆下油缸内的油筛清洗。A.
1000-2000
B.
2000-3000
C.
3000-4000
D.
4000-5000
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【单选题】No sooner _____ the boy fall into the pond than he ____ to his feet and went to the rescue.
A.
he had seen… jumped
B.
had he seen… jumped
C.
has he seen… is jumped
D.
did he see… had jumped
【单选题】There are studies indicating female with four different photopigments in a certain kind of cells have better color sensitivity than those with three different photopigments. What type of cell has the ...
A.
The rod cell
B.
The cone cell
C.
The Retina horizontal cell
D.
The photosensitive Retinal Ganglion Cells (pRGC)
【单选题】Hardly ______ he entered the classroom when the rain began to fall in big drops.
A.
he has
B.
has he
C.
he had
D.
had he
【简答题】He’s working hard for fear that he__________. A．should fall behind B．fell behind C．may fall behind D．would fall behind
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