The door, although supposed to be open, is now locked. 门,本应该开着,现在却关着。 我们本来应该八点钟到达这里,而我们却迟到了。 ___. You are not supposed to smoke on the bus. 你不可以在公共汽车上抽烟。 不定式有时用进行形式或完成...