is a best-known secret in success that get ready in much of our life and you may make the most of the opportunity．
A. What
B. As
C. It
D. That
网友回答
A. What
B. As
(答案→)C. It
D. That
解析：句意：成功最著名的秘密是一生做好充分的准备那么，你就可以充分利用人生的机会。A. What什么； B. As正如；C. It它，可以做形式主语或宾语； D. That那。It is a best-known secret in success that...相当于As is a best-known secret in success，....或者What is a best-known secret in success is that......。由句意可知选C。
考点: 考查代词的用法。