Yes, I just wanted to keep silent.

是的，我要保持沉默。

He warned her to keep silent.

他告诉她要保持沉默。

Do you know when to keep silent?

你知道什么时候该保持沉默吗？

He can keep silent 10 hours.

你能保持沉默长达10个小时。

You are wise to keep silent.

你保持沉默，这是明智。