Such animals as South China tigers are believed __________ ., for we've had ...

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问题 Such animals as South China tigers are believed __________ ., for we've had no track of them for ages.

选项 A.becoming extinct
B.to become extinct
C.to have been extinct
D.having been extinct

答案C

解析考查时态和语态。当believe为被动语态时,后面习惯接不定式。根据后半句“for we’ve had no track ofthem for ages”判断,时态应为现在完成时,extinct“绝种的,灭绝的”。故选C。
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