Select the most appropriate idiom to fill in the blank.
Jack took on three jobs at once but soon realised he had _____________.

Correct option is C

The most appropriate idiom to fill in the blank is "bitten off more than he could chew."
· Meanings of the given options:
· Bitten off more than he could chew: This idiom means taking on more responsibilities or tasks than one can handle.
· Cut corners: To do something in the easiest, cheapest, or fastest way.
· Taken it with a grain of salt: To view something with skepticism or not take it literally.
· Played by the ear: To improvise or do something without planning.
· Correct sentence: Jack took on three jobs at once but soon realized he had bitten off more than he could chew.