那只狗感到威胁时，背上的毛都竖了起来。

The dog's fur was ___bristling when it sensed danger.

他对那些无理的批评感到非常愤怒。

He was ___bristling at the unreasonable criticism.

猫的背部在受惊时会竖起短硬的毛发。

The cat's back was ___bristling with short, stiff hairs when it got scared.