Final answer:
Mark is dealing with 'role conflict', a type of tension arising from conflicting social roles, specifically related to his sister's revelation about her same-sex relationship versus his perceived obligation to his parents.
Step-by-step explanation:
Mark is experiencing a classic example of role conflict, a form of tension that occurs when a person faces competing demands stemming from different roles they play within their social circles. In this case, Mark's loyalty and obligation to maintain his sister's confidence clashes with a sense of duty to inform his parents about her situation, possibly due to family values or expectations.
The intensity of this dialectic tension is amplified by the personal nature of sexual orientation and the societal pressures associated with same-sex relationships. It's these kinds of competing pressures and expectations that create a complex scenario for individuals when dealing with sensitive matters about identity, orientation, and family dynamics.