The idiom “Get your act together” means to organize yourself and your activities in a more effective way in order to achieve something.

Example: He needs to get his act together if he is going to pass.

Hence, option B is the correct answer.

The idiom “Vanish into thin air” means to disappear suddenly in a mysterious way.

Example: At a stroke, he could make things vanish into thin air.

Hence, option C is the correct answer.

The idiom “Throw caution to the wind” means to stop caring about how dangerous something might be i.e. to start taking risks.

Example: He threw caution to the wind and dived into the water after the child.

Hence, option C is the correct answer.

The idiom “Once and for all” means now and for the last time; finally or completely.

Example: We need to settle this once and for all.

Hence, option A is the correct answer.

The idiom “Twist someone's arm” means to persuade or force someone to do something.

Example: We do not want to go the park for morning walk, but our parents twisted our arm.

Hence, option D is the correct answer.

The idiom “To call the shots” means to be the person who controls a situation.

Example: Everyone in the meeting agreed that it is up to Ramesh to call the shots.

Hence, option C is the correct answer.

The idiom “at a snail's pace” means very slowly.

Example: I set off at a snail’s pace to conserve my energy for later in the race.

Hence, option C is the correct answer.

The idiom “Bear the brunt” means to receive the main force of something unpleasant.

Example: Schools will bear the brunt of cuts in government spending.

Hence, option D is the correct answer.

The idiom “Behind closed doors” means without the public being allowed to attend or know what is happening; in private.

Example: The meeting between the two politicians held behind closed doors.

Hence, option D is the correct answer.

e.g. The party is at loggerheads with the president over public spending.

Hence, option B is the correct answer.