We are now in the age of great changes. Everything sometimes before it is felt.A. changeB

问题补充：

We are now in the age of great changes. Everything sometimes before it is felt.

A. change

B. had changed

C. has changed

D. changed

答案：

A. change

B. had changed

(答案→)C. has changed

D. changed

解析：整个句子用的都是现在时，所以排除BD选项。主语是“everything”故排除A选项。用现在完成时强调结果。句意：我们现在处在伟大的变革时代。常常是等到一切变化了我们才感觉到。