Select the most appropriate meaning of the given idiom.

Under a cloud

In suspicion, in disfavour or disgrace

The correct answer is In suspicion, in disfavour or disgrace. The idiom "under a cloud" means to be suspected of something wrong or to be in a state of disfavour or disgrace. It is often used to describe someone who has been accused of a crime or who is unpopular. For example, you might say "The politician was under a cloud after he was accused of corruption."

The other options are incorrect. "Without hiding a matter" is the meaning of the idiom "to be open and honest." "To look the lock with a key, carefully" is not an idiom. "To rebuke, to scold" is the meaning of the idiom "to give someone a piece of your mind."