Final answer:
Non-consensual intercourse is the most common type of activity in the sexual assault of men by men.
Step-by-step explanation:
The most common type of activity in the sexual assault of men by men is non-consensual intercourse. This refers to any sexual penetration or intercourse that occurs without the explicit consent of one party. It is important to note that sexual assault can take various forms and is not limited to any one type of activity.