A．(A) People using the Internet will soon be almost doubled.

B．(B) Population is exploding because of the Internet.

C．(C) Ten years ago, only rich people can afford to use the Internet.

D．(D) The Internet population will increase two fold in ten years.

通信站直流供电系统中，应采用（）与（）并联浮充的供电方式供电。