21.You see,I still have this pain in my back;this medicine the doctor gave me was supposed to make me feel better by now.
be supposed to的用法如下:
当be supposed to的主语是sb.时，意为“应该;被期望“，可以用来表示劝告、建议、义务、责任等，相当于情态动词should。如:
Teachers are supposed to treat ail students alike。
当be supposed to的主语是sth.时，意为“本应，本该“，用于表示“某事本应该发生而没有发生“。如:
The train was supposed to arrive an hour ago.
当be supposed to后接“have+过去分词“时，表示“本应该做某事而没做，，。如:
You are supposed to have handed in your homework by now.
be supposed to的否定结构为be not supposed to，常用于口语中，意为“不被许可;不应当“。如:
She was not supposed to be angry about that.