Proficiency Idioms and expressions : Answers (exercise 3 page 34 Gold Maximazer in the previous post).

Meanings source: thefreedictionary.com

1.- Mark's brother decided on the spur of the moment to

take a bus home.

Meaning: 

Adv.

1.

on the spur of the moment - on impulse; without premeditation; "he decided to go to Chicago on the spur of the moment"; "he made up his mind suddenly" suddenly

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2.- I have set my heart on an exotic foreign holiday.

set (one's) heart on

To be determined to do something.

moments-of-tranquility.com



3.- Sandra didn't get a wink of sleep/didn't sleep a wink

last night.

not sleep a wink  also not get a wink of sleep

to not sleep at all I was so excited last night - I didn't sleep a wink. I didn't get a wink of sleep on the plane.

equestriadaily.com


.
4.- The mistake only came to light when we counted the 

money.
come to light

Fig. [for something] to become known or to be discovered. Many surprises have come to light since then. Nothing new has come to light since we talked last.

fluid-radio.co.uk


5.- I don't mind lending you money but I draw the line at 

paying for a new car. 

draw the line (at something)

to set a limit at something; to decide when a limit has been reached. You can make as much noise as you want, but I draw the line at fighting. It's hard to keep young people under control, but you have to draw the line somewhere.

whatjeanlikes.com