so far,the shanghai world expo ____to be a great success as

so far,the shanghai world expo ____to be a great success as people expected.为什么填has proved 不是has been proved?

prove是个常用动词,也是一个多义动词.由于它的用法比较复杂,现归纳如下
一、prove作"证明;证实"解时,用法如下:
1.prove+名词/代词
He has proved his courage in the battle.他已在作战中证明了他的勇气.
This further proved the strength of our economy.这进一步证明了我们的经济实力.
Can you prove that?你能证实那一点吗?
2.prove+直接宾语(sth.)+to+间接宾语(sb.)
The difficulty was how he could prove his ideas to other scientists.困难在于他怎样向其他科学家证实他的想法.
Can you prove your theory to us?你能向我们证实你的理论吗?
3.prove+宾语+宾语补足语
(1)形容词作宾语补足语
They proved themselves wise and brave.他们证实自己机智、勇敢.
Facts have proved these worries groundless.事实证明,这些忧虑是没有理由的.
(2)名词作宾语补足语
She proved herself an able secretary.她证实自己是个能干的秘书.
He has proved himself a success.他已证明了自己是个成功者.
(3)动词不定式作宾语补足语
All this proved him to be an honest man.这一切都证明他是一个诚实的人.
The experiment proved his theory to be important to our research.实验证明他的理论对我们的研究是重要的.
4.prove+宾语从句
Galileo proved that the earth and all other planets move around the sun.伽利略证实地球和所有其它的行星都是绕太阳运转的.
But Einstein was able to prove that light coming from the stars was bent as it passed the sun.
然而爱因斯坦却能证明从恒星来的光线当其经过太阳时变弯曲了.
Can you prove where you were on May 10th?你能证实五月十日你在什么地方吗?
二、prove作"证明是;结果是;事实说明"解时,用作连系动词,可用于以下句型:
1.prove+形容词
The handbook proved most useful.这本手册证明很有用.
The medicine proved satisfactory.结果证明这药疗效令人满意.
2.prove+名词
She proved a very strict teacher.结果证明她是一位非常严格的老师.
His efforts, however, proved a failure.但他的努力结果都失败了.
3.prove+介词短语或副词
Perhaps this book will prove of some use to you in your studies.也许这本书会对你的研究有用处.
The power station was completed and proved up to standard.这座发电站建成了,证明质量符合标准.
4.prove+动词不定式
As time went on, Einstein's theory proved to be correct.随着时间的推移,爱因斯坦的理论证明是正确的.
She may prove to be the most suitable person for the job.结果她可能是最适合干这项工作的人.
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用作连系动词,无被动语态