55. Given: 
11. abstract class Vehicle{public int speed(){return 0；}} 
12. class Car extends Vehicle{public int speed(){return 60；}} 
13. class RaceCar extends Car{public int speed(){return 150；}}
 ...
 21. RaceCar racer = new RaceCar()； 
22. Car car = new RaceCar()； 
23. Vehicle vehicle = new RaceCar()； 
24. System.out.println(racer.speed() + ", " + car.speed()
 25. + ", " + vehicle.speed())； 
What is the result?
(A) 0, 0, 0
(B) 150, 60, 0
(C) Compilation fails.
(D) 150, 150, 150
(E) An exception is thrown at runtime.

答案：登入後查看
統計： A(0), B(2), C(1), D(0), E(0) #2722954