根据句意用括号内所给词的正确形式完成句子.

这里牵扯到prove的用法,你看完下面就明白了.
prove用法：
(一)可作系动词,后接(to be)＋名词/形容词,构成系表结构,意“结果是…,证明是”,没有被动语态.
The book proved (to be) interesting.
(二)作实义动词用法.
1、prove＋n.(作宾语),意“证明某事”,如：
The scientist finally proved the fact.那位科学家最终证实了那个事实.
2、prove＋that宾语从句
The fact proved that his statement was true.
事实证明他的说法是正确的.