What Is the Main Idea Behind Government Corporations

What is the main idea behind government corporations?

A) The government is able to provide certain services at a lower cost and higher quality than private companies.
B) There is demand for the services provided by the corporation, which serves an important public purpose.
C) Just as the government privatizes certain services, private companies shift a service over to the government's control.
D) The government has enough tax revenue to set up a company that provides a benefit to the public for free.