In the case of considering the cost, what is the most suitable deployment mode as follows?

An enterprise has deployed IP PBX, eServer and other equipment, now required the call contents of specific positions staff can be traced back, the number of employees in specific positions of less than 50.

In the case of considering the cost, what is the most suitable deployment mode as follows?
A . new added recording system deploymemt, the components of the recording system can be co-located
B . new added recording system deploymemt, recording servers deployed independently
C . new added UMS components
D . keep existing equipment can meet the demand

Answer: A