Click the Exhibit button. Given: ClassA a = new ClassA(); a.methodA(); What is the result? （）

A.harrier
B.shepherd
C.retriever
D.Compilation fails.
E.retriever harrier
F.An exception is thrown at runtime.

A.a
B.b
C.c
D.ac
E.abc

A.Alpha a = x;
B.Foo f = (Delta)x;
C.Foo f = (Alpha)x;
D.Beta b = (Beta)(Alpha)x;