单项选择题
What is the result？（）
A.hi hi B.hi world C.world world D.Compilation fails. E.An exception is thrown at runtime.
What is the result？（） A.2B.3C.4D.6E.7F.Compilation fail...
A.2 B.3 C.4 D.6 E.7 F.Compilation fails.
What is the result？（） A.2-1B.2-4C.2-5D.3-1E.3-4F.3-5G.C...
A.2-1 B.2-4 C.2-5 D.3-1 E.3-4 F.3-5 G.Compilation fails. H.An exception is thrown at runtime.
What is the result？（） A.Compilation fails.B.An exceptio...
A.Compilation fails. B.An exception is thrown at runtime. C.The variable first is set to null. D.The variable first is set to elements[0].
