He makes a rule to arrive at office on time which is to be carried out from next Monday.

问题补充：

He makes a rule to arrive at office on time, which is to be carried out from next Monday.

A. that

B. it

C. which

D. what

答案：

A. that

(答案→)B. it

C. which

D. what

解析：考查it用法。本题中it做形式宾语指代to arrive at office on time内容，其它选项无此用法，故选B。