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.
六级词汇讲解:
被动语态表示主动含义的用法在英语里很常见，但却与我们中国人的思维习惯相去甚远，考生需多加练习。分号后句子的意思是医生给我开的药现在应该可以使我感觉好些了。
英语六级考点归纳
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。
老师应该对所有学生一视同仁。
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.
火车本应在一小时之前到达。
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.
到现在你应该已经把作业交上来了。
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.
她本不该为那件事而生气的。