The salesman had to______the conversation in order to wait on a customer.

A．Because the world is becoming more and more noisy.
B．Because they have learned that noise is also a kind of pollution.
C．Because noise is an unwanted waste for human beings.
D．Because people knew little about the danger of noise before.

A．our society is becoming much worse than before
B．in our modem society it is hard to lead a quiet life
C．the old days were much happier than the present time
D．it is impossible for us to deal with noise as we did before