Select the most appropriate meaning of the given idiom.

Through thick and thin

under all circumstances

The most appropriate meaning of the idiom "through thick and thin" is under all circumstances. It means to support or stand by someone or something no matter what happens. The idiom is often used to describe a close friendship or relationship.

The other options are not correct.

• By unfair means: This is not the same as through thick and thin.
• Under extreme pressure: This can be part of what it means to go through thick and thin, but it is not the whole meaning.
• Going through pain: This can be part of what it means to go through thick and thin, but it is not the whole meaning.