The road construction is based on the agreement one of purposes is to ensure its complet

问题补充：

The road construction is based on the agreement, one of purposes is to ensure its completion on time.

A. which

B. whose

C. that

D. what

答案：

A. which

(答案→)B. whose

C. that

D. what

解析：句意：公路的建设是基于协议，其中的一个目的是确保按时完工。这里是非限制性定语从句，先行词是agreement，关系词在从句中作定语，that不能引导非限制性定语从句，what不能引导从句，whose可以在从句中作定语，表示某人的或某物的，故选B。