单项选择题

Such animals as South China tigers are believed ______, for we’ve had no track of them for ages.

A.becoming extinct
B.to become
C.to have been extinct
D.having been extinct
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单项选择题
Over the past decades, sea ice ______ in the Arctic as a result of global warming.
A.had decreased
B.decreased
C.has been decreasing
D.is decreasing
单项选择题
It was the second time he ______ to me. I would never trust him again.
A.lied
B.has lied
C.was lying
D.had lied
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