Choose the idiom/phrase that can substitute the highlighted group of words meaningfully:
My son was not well yesterday and today I'm feeling sick.

The correct idiom is (a) Under the weather.
Explanation:
"Under the weather" is an idiom used to express that someone is feeling ill or unwell. In the given sentence, the speaker is feeling sick, which fits the meaning of the idiom.
Corrected sentence:
"My son was not well yesterday and today I'm feeling under the weather."
Meanings of all options:
· Under the weather: Feeling ill or unwell.
· Call it a day: To stop working for the day.
· Face the music: To confront the consequences of one's actions.
· Break a leg: A way to wish someone good luck, especially in a performance.