Select the most appropriate meaning of the given idiom.

Up in arms

In rebellion

The most appropriate meaning of the idiom "up in arms" is >In rebellion or angry and ready to fight.<

This idiom is often used to describe people who are very angry about something and are willing to take action, such as protesting or fighting. It can also be used to describe people who are opposed to something, such as a new law or policy.

The other options are not correct.

• Begin fighting does not mean up in arms.
• Raise something does not mean up in arms.
• In unity does not mean up in arms.