According to the author, the breakthrough of this technology starts firm ______.

A．video conferencing will be an instance of superiority for some companies
B．video conferencing will be applied where communication is important
C．video conferencing will be a standard configuration for all people's computers
D．video conferencing still have a lot of room for improvement

A．the use of video conferencing is still a mystery for the general public
B．video conferencing may be as simple as telephones for communication
C．face to face relationship is important for customers and suppliers
D．video conferencing is especially popular with information technology firms