People will live 200 years old in the future.A. /B. beC. to beD. in

问题补充：

People will live 200 years old in the future.

A. /

B. be

C. to be

D. in

答案：

A. /

B. be

(答案→)C. to be

D. in

解析：句意:将来人们会活到200岁.不定式作宾语表示具体的将要进行的动作,结合语境可知选C.