Why will the administrator need to deploy vCenter Server on a Windows server?

An administrator is evaluating whether to deploy vCenter Server on a Windows server or on a vCenter Server appliance. The administrator has the following requirements:
A web browser will be utilized to manage the vSphere environment.
16 ESXi hosts will be deployed.
Licenses must be shared with a vCenter Server at another site.
An external Oracle 10g database server will be used to host the vCenter Server database.
Why will the administrator need to deploy vCenter Server on a Windows server?
A. Linked Mode is a requirement for the solution.
B. Oracle 10g is a requirement for the solution.
C. The vSphere web client is a requirement for the solution.
D. Management of more than 5 hosts is a requirement for the solution.