growl|growled|growling

猫在受到惊吓时会发出低沉的吼声。

The cat will ___growl when it feels threatened.

当我们靠近时，那只熊发出低沉的咆哮声。

The bear ___growled as we approached it.

这条狗正在低吼。

The dog is ___growling.