Given the following code， which method declarations， when inserted at the indicated position， will not cause the program to fail compilation？（）   public class Qdd1f {   public long sum（long a， long b） {  return a + b；  }   // insert new method declaration here  }  

• A、public int sum（int a， int b） { return a + b； }
• B、public int sum（long a， long b） { return 0； }
• C、abstract int sum（）；
• D、private long sum（long a， long b） { return a + b； }
• E、public long sum（long a， int b） { return a + b； }