According to me (Because the question is ambiguous) I would select Multi-user Because
A multi-user operating system is an operating system that allows multiple users on different computers or terminals to access a single system with one OS on it. These programs are often quite complicated and must be able to properly manage the necessary tasks required by the different users connected to it. The users will typically be at terminals or computers that give them access to the system through a network, as well as other machines on the system such as printers. A multi-user operating system differs from a single-user system on a network in that each user is accessing the same OS at different machines.
This family of OS has multi-user support Windows (NT/2000/XP/Vista)
We can also choose Real Time OS because
Windows does have a Windows Embedded family of products as Embedded Compact, formerly Windows Embedded CE and Windows CE,
I never heard like "I need a preemptive or non-Preemptive OS to do a particular task " .But you have definitely heard that we need a real time OS or Multi user OS (for online gaming ) so I would not choose these options. (just a common sense)