How Do Network Effects Benefit Established Businesses

How do network effects benefit established businesses?

A) Network effects allow consumers to find a variety of goods and services in one place.
B) Network effects both decrease transportation costs and encourage the concentration of many people and firms in a particular area, thereby leading to greater innovation by both existing firms and new ones.
C) Network effects don't benefit established businesses.
D) Network effects allow the established business to learn about its competitors, thus allowing it to lower prices and compete more effectively.