专四专八证书的有效期是多长时间？

According to Charles, people send messages via facsimile because ______.

A．it is cheaper and faster than ordinary mail

B．it can send things that could not be expressed by telex

C．it is faster and not much more expensive than mail

D．the Royal Mail could not reach places abroad

According to the passage, ______ has become the driving force for the development of telephone system?

A．information technologies

B．Internet

C．PC

D．convergence of telecommunications technologies

【6】