例如：
They supposed the paper to have been lost during the war. 他们认为那个文件在战争期间丢失了。
The police arrested him because he was supposed to have killed the lady. 警察逮捕了他，认为他杀死了那位女士。
suppose 可用于“ be supposed +不定式”的结构。
be supposed to do sth. = should do sth. 意为“应该 / 理应做某事”，表示被期望或被要求(按规则、惯例)做某事。
例如：
We are supposed to help each other. 我们理应互相帮助。(要求)
You are supposed to hand in your papers before class is over. 希望你下课前交卷子。(期望)