Answer: Contagion
Explanation:
Contagion is the phenomena through which a emotion, attitude,behavior etc is spread from one person to other person or group of people.This spread can be based on rumors, agenda, thought, point-of-view , suggestion,act of imitation etc.
According to the question,situation of Mark and his network of friends is depicting about contagion as his friends are buying he same car which Mark has bought and other three friend are also interested to buy it .Thus, the similar car buying network is established.
