UC知道过去完成时态与过去进行时态的主要区别
来源：百度知道 编辑：UC知道 时间：2024/05/16 04:45:50
为什么第二句是错的,请说明
the baby had been crying for 30 minutes when her mother came in.
the baby was crying for 30 minutes when her mother came in.
the baby had been crying for 30 minutes when her mother came in.
the baby was crying for 30 minutes when her mother came in.
......
for 30 m 表示已经哭了30分钟了，而且还在哭。
后面那句如果拿掉for 30 m就可以了。
FOR+一段时间 用现完
由于 when her mother came in.
是过去式所以这里用过完