class TestA {  public void start（） { System.out.println（”TestA”）； }  }  public class TestB extends TestA {  public void start（） { System.out.println（”TestB”）； } public static void main（String[] args） {  （（TestA）new TestB（））.start（）；  }  }  What is the result？（） 

A、 TestA

B、 TestB

C、 Compilation fails.

D、 An exception is thrown at runtime.

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