The idiom ‘In the nick of time’ refers to ‘just before the last moment when something can be changed or something bad will happen’. Only option C mentions the most relevant answer.

Hence, option C is the correct answer.

The idiom ‘turn over a new leaf’ refers to ‘to start behaving in a better way’. Option A mentions the most relevant answer.

Hence, option A is the correct answer.

The idiom ‘Once in a blue moon’ refers to ‘not very often’. Option B mentions the most relevant answer.

Hence, option B is the correct answer.

The idiom “stir up a hornets’ nest” means provoke trouble.

Ex :- It’s not that the management is not aware of few false bills here and there, but they don’t call it because it would expose many and stir up a hornet’s nest.

Hence, option B is the correct answer.

The idiom “the luck of the devil” means someone is extremely lucky.

Ex :- X: I’m alive today because I failed to board the plane that crashed yesterday. Y: You really have the luck of the devil.

Hence, option B is the correct answer.

The idiom 'hard nut to crack' means 'difficult problem'.

Hence, option B is the correct answer.

The idiom 'beating the air' means 'continuing to make futile attempts, fighting to no purpose'.

Hence, option C is the correct answer.

The idiom 'piece of my mind' means 'to voice one's disagreement or dissatisfaction, especially with another person; to scold or rebuke someone'.

Hence, option A is the correct answer.

The idiom ‘Explore every avenue’ means ‘To investigate or pursue every possible means to find a solution to a given problem’ which is similar to option C. Hence option C is correct.

The idiom "in the same boat" means to be in the same difficult circumstances as others.

Example: None of us has any money, so we’re all in the same boat.

Hence, option A is the correct answer.