Select the most appropriate meaning of the given idiom.

Be on cloud nine

To be in a state of extreme happiness

The most appropriate meaning of the given idiom "be on cloud nine" is to be in a state of extreme happiness.

This idiom is often used to describe someone who is feeling very happy and content. It is thought to have originated from the idea that clouds are often associated with happiness and peace. For example, you might say "I'm on cloud nine after getting a promotion at work." This means that you are feeling very happy and excited about your promotion.

The other options are not as accurate descriptions of the meaning of the idiom.

• To be able to climb higher: This is a literal description of being able to climb to a higher altitude.
• To dream of clouds: This is a literal description of dreaming about clouds.
• To think about something unrealistically: This is more accurately described by the idiom "to have unrealistic expectations."