Recall the Application About the Wireless Phone Service Provided by Thousands

Recall the Application about the wireless phone service provided by thousands of entrepreneurial women in Pakistan to answer the following question(s) .
-Recall the Application. What makes the wireless telephone market in the United States NOT perfectly competitive?

A) There are many buyers and many sellers in the United States.
B) It is very expensive to enter the market in the United States.
C) Wireless phone calls are a standardized product.
D) All of the above are correct.