The truck started going backward, and building up speed on the way down.

那辆货车开始慢慢地往山下后退，并在溜坡的过程中速度越来越快。

youdao

The truck started going backward, and building up speed on the way down.

那辆货车开始慢慢地往山下后退，并在溜坡的过程中速度越来越快。

youdao