The great scientist became world-known in the early 1970s,______ he and another scientist made new discoveries about black holes.
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which
B
where
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when
D
then
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___ difficulty you may have, we will always fight along with you.
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A
What
B
How
C
Whatever
D
However
The exciting news has spread all over the world______the satellite around the moon succeeded in returning to the earth.
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which
B
that
C
whether
D
what
19.They talked about things and persons ___ they remembered in the school.
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who
B
which
C
that
D
what
But when I got _______ the town ought to have been, all I found was a gas station．
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where
B
which
C
what
D
that