Mr. hughes heard what sounded like cries for from a swimmer located 30 yards from the ocean shoreline. he continued walking along the beach, however, because he figured that one of the many swimmers in the vicinity would provide if it was needed.
his reaction best illustrates the dynamics involved in:

a. the fundamental attribution error.
b. group polarization.
c. the bystander effect.
d. the mere exposure effect.

The bystander effect

Explanation:

The bystander effect term was proposed by Darley and Latane in social psychology. The bystander effect is seen when an individual discourages from the helping of another person who is in need.

It happened because of the presence of others. Bystander effect increased with the number of individuals present at the place and decrease when the number of people decreased. Latane and Darley invented this term when in new-york a woman 28-year-old was stabbed by her boyfriend in front of other people and no one assists to help her because of the bystander effect.  

Thus in the above statement, Mr. Hugh faces the same condition in the situation when someone was crying for help and he assumed many swimmers are there to help her if she needed it.