Select the most appropriate meaning of the given idiom.

To smell a rat

To have reason to suspect

The most appropriate meaning of the idiom "to smell a rat" is to have reason to suspect.

It is a colloquial expression that means to have a feeling that something is wrong or suspicious. It can be used to describe a person, a situation, or a plan. For example, you might say that "I smell a rat in this deal" or "I'm starting to smell a rat with my boss."

The other options are incorrect:

• To have reason to know the presence of a rat: This is a literal meaning of the idiom, but it is not the most common or appropriate meaning.
• To know the smell of a rat: This means to be familiar with the smell of a rat. It is not idiomatic and is not used in the same way as "to smell a rat."
• To learn the smell of a rat: This means to become familiar with the smell of a rat. It is not idiomatic and is not used in the same way as "to smell a rat."