你小声嘀咕着咒骂。

You muttered curses ___under ___your ___breath.

你一直小声嘀咕着，'我们一定走错路了。'

You kept muttering, "We must have taken a wrong turn," ___under ___your ___breath.

如果你小声说话，别人很难听清。

If you speak ___under ___your ___breath, it's hard for others to understand.