A train approaches a tunnel AB. Inside the tunnel is a cat located at a point that is `3/8` of the distance AB measured from the entrance A. When the train whistles, that cat runs. If the cat moves to the entrance A of the tunnel, the train catches the cat exactly at the entrance. If the cat moves to the exit B, the train catches the cat at exactly the exit. The ratio of the speed of the train to that of the cat is of the order `3:1` b. `\ 4:1` c. `5:1` d. none of these