Choose the correct meaning of the underlined idiom from the options given below :

We should guard against our green - eyed friends.

jealous

The correct meaning of the underlined idiom is jealous.

The idiom "green-eyed monster" is a reference to the Greek myth of Medea, who was so jealous of her husband Jason's new wife, Creusa, that she killed Creusa and her own children. The idiom is often used to describe someone who is feeling envious or resentful of someone else's success or possessions.

The other options are incorrect.

• Rich means "having a lot of money."
• Mad means "mentally ill."
• Enthusiastic means "showing great interest and excitement."