High-speed trains travel at 300 kilometers an hour, which is about ______normal trains.

A．four times the speed as                          B．the speed four times of

C．four times as the speed of                  D．four times the speed of

High-speed trains travel at 300 kilometers an hour, which is about         normal trains.

A．four times the speed as                                B．the speed four times of

C．four times as the speed of                        D．four times the speed of

High-speed trains travel at 300 kilometers an hour，which is about      normal trains．

1. A.
   four times the speed as
2. B.
   the speed four times of
3. C.
   four times as the speed of
4. D.
   four times the speed of

High-speed trains travel at 300 kilometers an hour，which is about　 normal trains.

A.four times the speed as　　　　　　　　　　 B.the speed four times of

C.four times as the speed of 　　　　　　　　 D.four times the speed of

High-speed trains travel at 300 kilometers an hour，which is about      normal trains．