I believe you have tried your best and you can come to the top of the class.A. that；/B.

问题补充：

I believe you have tried your best and you can come to the top of the class.

A. that；/

B. /; /

C. /; that

D. how; that

答案：

A. that；/

B. /; /

(答案→)C. /; that

D. how; that

解析：这题考查宾语从句的用法：believe后面接了两个宾语，第一个that可以省，第二个不可以省。选C。