Compile error: cannot declare Vehicle reference

Creating References Using Inheritance Hierarchies

AP Computer Science A· difficulty 2/5

public abstract class Vehicle {
    public abstract int wheels();
}
public class Bike extends Vehicle {
    public int wheels() { return 2; }
}
// Usage:
Vehicle v;
v = new Bike();
System.out.print(v.wheels());

What is printed?

A
$Runtime error$
B
$Compile error: cannot declare Vehicle reference$
C
$0$
D
$2$
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Explanation

Abstract classes can be used as REFERENCE types even though they cannot be instantiated. v refers to a Bike, and dispatch returns 2.

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