A．It is because the Cathedral of Norte-Dame in Paris had many bell-towers and could tell time to people that the writer regards it as an engine of mass communication.
B．From Cathedrals to books to computers the technology of communication has become more convenient, reliable and fast.
C．Every time when a new communication means triumphed over the old, it divided mankind into two groups.
D．Computer industry has been trying hard to make people accept computers.