题目内容:
Such animals as South China tigers are believed __________ ., for we've had no track of them for ages.
A.becoming extinct B.to become extinct C.to have been extinct D.having been extinct
参考答案:
答案解析:
Such animals as South China tigers are believed __________ ., for we've had no track of them for ages.
A.becoming extinct B.to become extinct C.to have been extinct D.having been extinct