have的過去式是什么？

　　例句

　　This is too big ─ have you got a small one?

　　這個太大——有沒有小的'？

　　The latest model has over 100 new features.

　　最新的款式有100多種新特色。

　　The two groups of children have quite different characteristics.

　　這兩組兒童具有截然不同的特點。

　　Now she won't have to go out to work any more.

　　現(xiàn)在她不必再出去工作了。