答案：B

解析：

When the speed of a train in miles per hour is multiplied by the travel time in hours,the distance traveled by the train is obtained.The distance that the first train travels is miles per hour times hour,which ismiles.Using the variable for the travel time, in hours, of the second train,the distance that the second train travels is miles per hour times hours,which is miles.Since the two trains travel the same distance,which gives hours,the travel time of the second train.