A.The gain functionality applies to outbound audio packets. Distortion is created when an external participant causes echo. 
B.The distortion is unrelated to the gain functionality. Rather, it is a result of the company trying to maintain too many conference calls at one time. 
C.This functionality cannot discriminate between a local VoIP source that requires volume gain and a CO-powered PSTN source that does not require volume gain. 
D.This functionality cannot discriminate between a remote VoIP or Foreign Exchange Office source that requires volume gain, and a remote VoIP or IP phone that does not require volume gain.