Sofarthereisnoproof（）spaceshipfromotherplanetsdoexists.
A. which
B. that
C. how
There’snopoint（）aboutthequalityofproductstotheshop-assistant.
A. topoint
B. pointing
C. pointed
Onlyafterhundredsofexperiments()succeedinsolvingsuchacomplexproblem.
A. dothey
B. they did
C. didthey
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