Answer: Postconventional level
Explanation: The Postconventional stage of moral development is the third and final level of Kohlberg's moral development taxonomy. Individuals at this stage or level are more guided by ethical rights, values, duties as well as moral principles.
Helen decided that the moral thing to do is not to cheat in the test but do her best on her own merit, with this moral principles guiding her, she is probably at the postconventional level of the Kohlberg's moral development taxonomy.