be supposed to的用法

be supposed to相当于be expected or required to,意为"被期望或被要求做某事;(有责任、有义务)应该做某事;(按规定)应该做某事",be要与句子的主语在数、格上保持一致,to后面接动词原形。例如:You are supposed to be there before eight.你应该在8点钟以前到那里。