Which combination of port types can exist on the root bridge?

A root bridge in an RSTP network is connected to other neighboring bridges using point-to-point links.
Which combination of port types can exist on the root bridge?

A.
There can be some combination of designated ports and alternate ports.

B.
There can be some combination of root ports and alternate ports.

C.
All ports will be designated ports

D.
All ports will be root ports