Network managers have long (140) practical voice-over-IP (VOIP) solutions. VOIP (141) ease network management and decreases costs by converging a company’s telephony and data infrastructures into one network. And a VOIP solution implemented at a company’s head-quarters with far-reaching branch offices can (142) tremendous amounts of (143) in long distance phone bills, provided that solution delivers POTS-like voice (144) over the Internet.
A．frequency
B．length
C．quality
D．quantity