A 在 assume， believe， consider， feel， know， suppose， understand 等之后可接宾语+ to be：I consider him to be the best candidate． 我认为他是最佳人选。但that+普通动词的结构比这常用得多：I consider that he is the best candidate．（译文同上。）宾语+不定式与 think， estimate和 presume 等动词连用是极少见的。这种表达方法常用that从句来代替：I think that he is the best player．我认为他是最好的演奏家／演员／运动员。It is estimated that the vase is 2，000 years old． 据估计这个花瓶有两千年历史。B 然而，如果这些动词是以被动形式出现的，那么它们后面常常带不定式而不是带that结构：He is known to be honest．相当于：It is known that he is honest．众所周知，他是个老实人。He is thought to be the best player相当于：It is thought that he is… 人们认为他是最好的演奏家／演员／运动员。This vase is estimated to be 2，000 years old．据估计这个花瓶有两千年历史。C 注意suppose的被动态时往往有责任或义务之意：You are supposed to know the laws of your own country．你应该懂得你们自己国家的法律。相当于：It is your duty to know／You are expected to know…你有义务懂／人们认为你该懂……D 在这些动词后面也可以用不定式的进行式：He is thought to be hiding in the woods． 人们以为他正躲在森林里。（人们认为他正躲着。）He is supposed to be washing the car． 他应该在洗车。（他该正在洗它。）E 如果想到的是早先发生过的动作，则用不定式的完成式：They are believed to have landed in America．人们相信他们在美洲上了岸。（据信他们已登上了。）supppose+不定式的完成式不一定有责任或义务之意。They are supposed to have discovered America．相当于：It is thought that they did． 人们认为是他们发现了美洲。但 You are supposed to have read the instructions（你应已看过操作说明）通常意味着你本应看过。（关于动词的被动式之后的不定式结构，另参见第306节。）