When Considering VoIP (Voice Over Internet Protocol) Systems, Which Is

When considering VoIP (Voice over Internet Protocol) systems, which is true?

A) Because of the complexity and expense of VoIP systems, most companies are upgrading or replacing their existing telephone systems when they become obsolete rather than using VoIP.
B) Companies using traditional telephone systems need to invest in significant upgrades to their data network in order to support VoIP traffic and guarantee call quality and network reliability.
C) Since VoIP systems transmit voice communications differently than e-mail and instant messaging systems, organizations must decide which method of transferal will be most beneficial to them.
D) Benefits of VoIP include enabling of screen pops, the ability to link local service desks and analysts working at home, increased agent mobility, and reduced telephone company fees.