A.Auto Attendant answers calls and directs them to voice mail if the extension entered does not answer the call. 
B.Auto Attendant is designed to provide operator-like functionality for after-hour, weekend, and holiday operations. 
C.Auto Attendant will answer calls and will allow the caller to self-direct by entering the extension, entering the name, or dialing 0 for the operator. 
D.Auto Attendant will answer calls, collect digits, and forward calls to the operator for further processing.