Answer:
Independently run private sector companies.
Step-by-step explanation:
Government corporations are independently run private companies established either by act of Congress or executive order under state incorporation law which provides services to the public and produce revenue that would cover it's running cost. Corporations are not established to make profit but could generate revenue through the services rendered.
The aims of government corporation is to take care of those areas difficult for government to handle, provide services to masses and also ensure the that the government is operating maximally and efficiently. An example of government corporation is the US Post office, which charges fees for service rendered to the public hence create revenue to meet it's running cost.