10. interface Foo {} <br /> 11. class Alpha implements Foo {} <br /> 12. class Beta extends Alpha {} <br /> 13. class Delta extends Beta { <br /> 14. public static void main( String[] args) { <br /> 15. Beta x = new Beta(); <br /> 16. // insert code here <br /> 17. } <br /> 18. } <br /> Which code, inserted at line 16, will cause a java.lang.ClassCastException?() 
A、 Alpha a = x;
B、 Foo f= (Delta)x;
C、 Foo f= (Alpha)x;
D、 Beta b = (Beta)(Alpha)x;