Final answer:
The abbreviation for minor used in the context of travel for ages 15-17 traveling alone is 'MNR'. This term is widely used in the travel industry.
Step-by-step explanation:
The abbreviation for minor, specifically referring to those aged 15-17 years old when traveling alone, is commonly MNR, which stands for 'Minor'. This term is often used by airlines and in travel industry documentation to denote a young traveler who is not accompanied by an adult. The options given, MIN could generally represent 'minor,' but MNR is more specifically used for unaccompanied minors in the context of travel.