better late than never is correct because better late than never means doing something late is still better than not doing it at all.

This idiom or phrase is useful because it helps students understand the intended meaning beyond the individual words.

Examples: You submitted the project after the deadline, but better late than never. He finally apologized after a week; better late than never.

The sentence talks about completing work later than expected, so the other choices do not fit the time-related meaning.