如果你不守口如瓶，就会有麻烦。

If you don't ___keep ___your ___mouth ___shut, there'll be trouble.

她尽力保持沉默，但自己是唯一知道真相的人让她不安。

She made every effort to ___keep ___her ___mouth ___shut but it disturbed her to be the only one to know the truth.

为了保护朋友，他决定对这件事守口如瓶。

To protect his friend, he decided to ___keep ___his ___mouth ___shut about the incident.