The most commnonly used OS is ___.
MS-DOS
Windows
Mac
Linux

Windows

Explanation:

The most commonly used OS today is Microsoft Windows. Microsoft's founder and President Bill Gates created the operating system way back then.

Windows is the default standard in most computers you see today and is in use in across millions/billions of devices.

Mac and Linux are similar; Mac OS, or SierraOS, is a custum Linux base OS. Both of these operating systems are popular now, but still not as widespread popular as Windows.

SierraOS only targets Mac/Apple Users. Linux targets coders.

the answer is d. splog

the major difference between the two is the objective and the reward of the game. candy crush has a puzzle theme with the objective of meeting a specific quota of points or objects, you are able to gain access to the next level and compete with peers on the process. on duolingo the objective is rather different, you are given sets of questions for you to answer for you to move to the next level and as for the reward, you are able to learn available language as this is an app developed to teach the user about other languages.