用重影点法判断相交问题的可见性，只需选择一个重影位置作判断。
查看答案
在线面间相交问题的可见性判断中，特殊位置平面的积聚性投影涉及的投影不需判断可见性
A. 对
B. 错
Ellen was absent this morning, she had her teeth _____.
A. filling
B. filled
C. to fill
D. fill
If it ______ sunny tomorrow, I ____ boating.
A. is go
B. will be, go
C. is, will go
D. will be, will go
Without the air to hold some of the sun's heat, the earth at night ____ for us to live.
A. would be freezing cold
B. will be freezing coldly
C. would be frozen cold
D. can freeze coldly
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