jam的过去式和过去分词

　　例句：

　　The fruit can be made into jam.

　　这种水果可以制成果酱。

　　People are fed up with all these traffic jams.

　　人们厌烦这么多的交通堵塞。

　　The valve has jammed shut.

　　阀门给卡住了打不开。