While walking through central park, mark sees a man being attacked and mugged. there are many people around the scene, and many of these people are holding phones. mark is concerned for the man, but ultimately does nothing. mark's actions can be explained by the concept

Mark's actions can be explained by the concept of the difussion of personality

Explanation:

Mark was not able to act and help the man because there were other people present and he assumed that someone else had already helped or will help the man. The concept of the difussion of personality states that a person is less likely to act when in presence of other people.

the diffusion of responsibility

Explanation:

Marks actions can be explained by the concept of the diffusion of responsibility.

i think it is the third one.