Which of the following is true about file formats? Open file formats may be either free or proprietary.

Open file formats are always free.

Free file formats may be either open or closed.

Proprietary files are always closed.

answer; i believe the correct answer is (psychological pricing);

system programmer option d is correct

because an operating system is software that manages computer hardware and system resources.

i believe the two important functions that skype uses are nat traversal and user location.good luck        

explanation:

lick on your profile and select log out on that device