Which two statements are true about the Web Logic Cluster?

Which two statements are true about the Web Logic Cluster?

A.
Clustered Servers capacity can be increased by adding new server instance to the cluster
on an existing machine.

B.
Clustered Servers can be on a same or different machine with same operating system
only

C.
Clustered Servers can only be on a same machine with same or different operating
system

D.
Clustered Servers can be on a same or different machine with same or different operating
system