What is the output？（）

A.Compilation fails.
B.An exception is thrown at runtime.
C.The attribute id in the ItemTest object remains unchanged.
D.The attribute id in the ItemTest object is modified to the new value.
E.A new ItemTest object is created with the preferred value in the id attribute.

A.public void foo（）{ }
B.public int foo（）{return 3；}
C.public Two foo（）{return this；}
D.public One foo（）{return this；}
E.public Object foo（）{return this；}

A.3
B.23
C.32
D.123
E.321
F.Compilation fails.
G.An exception is thrown at runtime.