Select the most appropriate meaning of the given idiom.

Keep a civil tongue

Speak with great politeness

The most appropriate meaning of the idiom "keep a civil tongue" is speak with great politeness.

The idiom means to be polite and respectful in your speech, even when you are angry or upset. It is a way of showing that you value the other person's feelings and that you want to avoid conflict.

For example, you might say "I'm trying to keep a civil tongue, but it's hard when you're being so rude." or "I know you're angry, but please keep a civil tongue."

The other options are not as appropriate. To maintain silence when needed is not the same as speaking with great politeness. Arguing with soft words can still be rude, depending on the words used. And expressing dissent mildly does not necessarily mean speaking with great politeness.