What is "a highly unreasonable omission or misrepresentation involving an extreme departure from the standards of ordinary care that a practitioner should observe under the circumstances"?

The correct answer is reckless conduct.

Reckless conduct is the term which refers to someone's actions which deviate from what was prescribed. So, when someone does something they were not supposed to do or fails to do something they were supposed to do, that will count as reckless conduct or behavior.