10. interface A { void x（）； }  11. class B implements A { public void x（） { } public voidy（） { } }  12. class C extends B { public void x（） {} }  And：  20. java.util.List list = new java.util.ArrayList（）；  21. list.add（new B（））；  22. list.add（new C（））；  23. for （A a：list） {  24. a.x（）；  25. a.y（）；；  26. }  What is the result？（） 

• A、 The code runs with no output.
• B、 An exception is thrown at runtime.
• C、 Compilation fails because of an error in line 20.
• D、 Compilation fails because of an error in line 21.
• E、 Compilation fails because of an error in line 23.
• F、 Compilation fails because of an error in line 25.