‏Which behavior would best describe someone who has integrity ? a ) Alerting a supervisor when a coworker comes in late b ) Putting off tough tasks until the last minute c ) Following through on a promise d ) Signing in for a coworker who's running late

I would say C) Following through on a promise.

Explanation:

Integrity: The quality of being honest and having strong moral principles; moral uprightness.

When you promise someone, you have the ethical integrity to be bound by your words.  When someone failed to keep their word or break promises, his or her reputation was damaged. Also, a lack of trustworthiness meant that people didn’t do business with them.