经过多年的努力，他们终于还清了抵押贷款。

After years of effort, they finally ___paid ___off their mortgage.

他计划在年底前还清信用卡债务。

He plans to ___pay ___off his credit card debt by the end of the year.

我们花了很长时间才还清汽车贷款。

It took us a long time to ___pay ___off the car loan.