Which of These Defines the Main Difference Between Microsoft and Linux

Multiple Choice

Which of these defines the main difference between Microsoft and Linux?

A) One is proprietary and only people at the company work on it; the other one is open-source and anyone in the world can contribute to it.
B) One is only sold in the U.S.and the other one is sold globally.
C) One can be used on any device and the other one only works on laptops.
D) One is priced for individual use and the other one is only for commercial use.