问题补充：
The suggestion they all objected to to be effective finally.
A. proving
B. prove
C. had proved
D. proved
答案：
A. proving
B. prove
C. had proved
(答案→)D. proved
解析：句意：他们都反对的那个建议最后证明是有效的。这里they all objected to是定语从句，先行词是suggestion，关系词是作宾语，给省略掉了；这里缺少的是谓语动词，故排除A；根据objected用的是过去式，可知答案应是D。
