The idiom, ‘a cold fish’ is used to denote a hard-hearted person who shows no emotion.

Example: He didn't really show much emotion – he's a bit of a cold fish.

Hence, option A is the correct answer.

The idiom “mad as a hatter” refers to someone who is completely crazy; abnormal or insane.

e.g. My grandfather came back from the war as mad as a hatter because of all the horrible things he saw.

Hence, option C is the correct answer.

The idiom “have one’s hands full” means to be very busy. 

e.g.  I can't do the job—I've got my hands full at my desk.

Hence, option C is the correct answer.

Let's first see the meanings of the idioms given in the options:

Wrap one’s head around = to comprehend something that one considers challenging or confusing.

Cry one’s eyes out = weep bitterly and at length; shed tears.

Run out of stream = to gradually lose energy or enthusiasm.

Bark up the wrong tree = to be wrong about the reason for something or the way to achieve something.

Hence, option D is the correct answer.

Example: In any relationship, you are expected to stick together through thick and thin.

Hence, option D is the correct answer.

The idiom "to fan the flames” means to make a feeling such as anger, hate etc. worse.

e.g. She already found him attractive, but his letters really fanned the flames.

Hence, option B is the correct answer.

The idiom "Spick and span” means neat and clean.

Example: We should keep our surroundings spick and span for germ-free ambience.

Hence, option C is the correct answer.

The meaning of the given idiom “to take a chill pill” is something that has a relaxing or calming effect.

E.g.: The police officer told Jim to take a chill pill and answer the questions.

According to the given options, the idiom can be defined as to calm down.

Hence, option B is the correct answer.

The given idiom “caught red-handed” means to discover someone while they are doing something bad or illegal.

E.g.: He was caught red-handed taking money from the till.

Hence, option A is the correct answer.