單項選擇題

1. class super { 
2. public float getNum() {return 3.0f;} 
3. } 
4.   
5. public class Sub extends Super {
6.  
7. }  
Which method, placed at line 6, will cause a compiler error?()  

A.  Public float getNum()   {return 4.0f; }
B.  Public void getNum ()  { }
C.  Public void getNum (double d)   { }
D.  Public double getNum (float d) {retrun 4.0f; }

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