问题描述: It has been proved that his theory is practical 怎么变为 His theory has been proved ( )如题 1个回答 分类:英语 2014-12-05 问题解答: 我来补答 to be practical 再问: practical 不是形容词吗?那不用改为ed形式? 再答: to be practical 就对了。不是verb,不用加ed的哦。 展开全文阅读