Such animals as South China tigers are believed

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

becoming extinct

to become extinct

to have been extinct

having been extinct

答案及解析：本题考查时态和believe的用法C选项，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 of them for ages”判断，时态应为现在完成时。extinct“绝种的，灭绝的”。综上，C选项正确。A选项，与题意不符，故排除。B选项，与题意不符，故排除。D选项，与题意不符，故排除。故正确答案为C 项。