我看到他有一把刀，立刻后退了。

I saw he had a knife and ___backed ___off immediately.

如果他试图后退，疯狗会杀了他。

Mad Dog would kill him if he tried to ___back ___off.

那只凶猛的狗咆哮着，所以我慢慢后退以避免冲突。

The aggressive dog growled, so I slowly ___backed ___off to avoid a confrontation.