be動詞的用法：做助動詞

　　助動詞be 有兩個基本用法，一是與謂語動詞一起構(gòu)成各種時態(tài)，二是構(gòu)成被動語態(tài)。

　　1、“be + 現(xiàn)在分詞組”成各種進行式時態(tài)。例如：

　　Tony's maid is washing his new car.

　　The children are playing in the field.

　　Samuel was eating when I came in.

　　We have been living here since 1959.

　　This time next day they will be sitting in the cinema.