Select the most appropriate meaning of the underlined idiom in the given sentence.

I always smell a rat when John says that he is going out for extra classes.

Suspect trickery or deception

The most appropriate meaning of the underlined idiom "smell a rat" in the given sentence is suspect trickery or deception.

The idiom "smell a rat" is used to describe someone who has a feeling that something is wrong or suspicious. In the given sentence, the speaker is saying that they always suspect that John is lying when he says that he is going out for extra classes.

The other options are not as appropriate meanings for the idiom "smell a rat":

• Reveal a secret: This idiom means to tell someone something that is supposed to be kept confidential.
• Trust completely: This idiom means to have complete confidence in someone.
• Say something stupid: This idiom means to say something that is foolish or nonsensical.