What does this idiom mean: "to save the day"?

Test No. [color=blue]incompl/inter-38 “Save the Day”, question 10

Despite all the problems and difficulties Charlie turned up at last minute and the day.

(a) caught
(b) hit
© saved
(d) took

Test No. [color=blue]incompl/inter-38 “Save the Day”, answer 10

Despite all the problems and difficulties Charlie turned up at last minute and saved the day.

Correct answer: © saved

Your answer was: [color=green]correct
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save the day in other words pls…

Meaning: find a solution/solve the problem.