An occulting light is one in which （）.
A. the period of darkness exceeds the period of light
B. there is only a partial eclipse of the light
C. the periods of light and darkness are equal
D. the period of light exceeds the period of darkne
查看答案
关井时应避开闸板防喷器关在（）。
A. 钻杆接头
B. 钻杆本体
C. 钻杆外加厚部分
D. 加重钻杆外加厚部分
E. 加重钻杆内加厚部分
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