(与动词be，seem，appear 连用时，代替句中的主语)(used to introduce a clause or sentence)：T～is a letter for you. 有你一封信。T～are several different kinds of pepper. 胡椒有几种不同种类。T～don't seem to be any mistakes in this. 这个似乎没有什么错。T～appeared to be nobody in the classroom. 看来教室里没有人。T～were staff meetings and a press conference daily. 每天都举行全体员工会和记者招待会。T～was (or were) a horse and a cow in the pasture. 牧场上有一匹马和一头牛。T～was (or were) a glass，two plates，and a teapot on the shelf. 架子上有一个杯子，两个盘子和一把茶壶。