to his disappointment,the opinion he had stuck to turned out wrong

题目

to his disappointment,the opinion he had stuck to turned out wrong
to turned 为什么不是to be turned ··
他坚持的意见被证明是错误的·· 不是应该用被动语态吗?求赐教!
the opinion he had stuck 是个定语从句我知道
在这里面缺少的是谓语动词··
the opinion he had stuck to turned out wrong
这里面的 turned 是动词一般过去式吗?

答案