Answer:
Obsessive-compulsive disorder
Step-by-step explanation:
Obsessive-compulsive disorder is a mental disorder that causes people to perform certain routines over and over again.
They have an unending urge to keep doing the same action repeatedly. The urge to the actions is so strong that it affects the person's ability to function.
Here, Mark spends a lot of time washing his hands so his symptoms indicates obsessive-compulsive disorder.