Why must an unmanaged desktop be registered with View Connection Server before it can be added to a pool?

Why must an unmanaged desktop be registered with View Connection Server before it can be added to a pool?

A.
The View Composer will not be able to create linked clones in the pool.

B.
The desktop must be known to vCenter Server to be seen by the Connection Server.

C.
The View Connection Server must remotely install View Agent before adding the desktop to the pool.

D.
The View Connection Server must know the FQDN or IP address of the desktop before it can add it as a source.