Which of the following features does a PBX/Key System have that two-line phones do not?

Which of the following features does a PBX/Key System have that two-line phones do not?

A.
The ability to route a call to a specific phone based on caller-id.

B.
The ability to place one line on hold and answer the other.

C.
The ability to create a 3-way call using both phone lines

D.
Receive and track caller-id per phone line.