找出错处并翻译各句
1.They are putting up the scaffolding.

2.You used to go swimming when you were at

college,usedn't you?
usedn't能否换为didn't

3.They fould that a stream had formed in the field.

Hi, 我没有把握，所以仅供参考吧

1. They're putting up scaffolding. (不觉得有什么特别不对的地方，也许是多余的冠词吧--好像They're pouring the water, the可以去掉。)

他们在搭建外墙支架。

2. 我只见过用didn't来反问used to的例子，感觉上usedn't好像不存在吧。（i.e. 换成didn't you）

你上大（美）\中（英）学的时候经常游泳是吗？

3. They found that a stream had formed in the field. (不会只是拼写吧?)

他们发现地里已经汇流了一条小溪。