Correct Answer: Going with his tail between his legs

Solution : The correct choice is the fourth option.

This phrase refers to someone leaving a situation in a cowardly or embarrassed manner, often because he has been proven wrong or feels ashamed.

The meanings of the other options are as follows:

• Flogging a dead horse means continuing a futile effort or trying to achieve something that is impossible or already settled.
• Gliding the pill isn't a commonly used idiom. It might be a variation or a less-known phrase. "Gliding the pill" could possibly mean to make something unpleasant seem more acceptable or easy to swallow.
• Falling flat means to fail completely or to be unsuccessful in an attempt or endeavour. It often refers to something lacking impact or not having the intended effect.