1.连系动词be后可根据情况接不定式作表语
My dream is to be a scientist.我的梦想是当一名科学家。
My plan was to go from London to Paris.我计划从伦敦去巴黎。
I was to have seen Mr Kay.我本要去见凯先生的。
2.seem，appear，prove，turn out，grow等词后可接不定式短语作表语
The man seemed to be ill.这个人好像病了。
He appears to know this.他好像知道这一点。
The plan proved to be useful.这个计划证明是有用的。
The weather turned out to be fine.天气结果很好。
He has grown to like studying English.他渐渐喜欢学英语了。
【提示】 若所接to be不定式为，通常可省略to be。
3.sound，smell，feel，taste，become后接形容词作表语，而不接不定式
This flower smells very sweet.这朵花闻起来很香。
【辨析】
【误】These oranges taste to be good.
【正】These oranges taste good.