In a Class of 10 Students,two of the Students Owned

Multiple Choice

In a class of 10 students,two of the students owned cell phones.Hence,only these two students could send text messages to each other in the class.A few days later,two more students got their own cell phones.This increased the habit of texting via phones.In a few months' time,all the students in the class got cell phones and thus,cell phones became more valuable in their class.Which of the following phenomena had occurred in the class?

A) Network internality
B) Network externality
C) Supply side economies of scale
D) Negative network effect