class ClassA { 
public int numberOfinstances； 
protected ClassA（int numberOfinstances） { 
this.numberOflnstances = numberOfinstances； 
} 
} 
public class ExtendedA extends ClassA { 
private ExtendedA（int numberOfinstances） { 
super（numberOflnstances）； 
} 
public static void main（String[] args） { 
ExtendedA ext = new ExtendedA（420）； 
System.out.print（ext.numberOflnstances）； 
} 
} 
Which is true？（） 

interface A { public int getValue（） } 
class B implements A { 
public int getValue（） { return 1； } 
} 
class C extends B { 
// insert code here 
} 
Which three code fragments， inserted individually at line 15， make use of polymorphism？（）