单项选择题
What is the result？（）
A.0 B.1 C.4 D.Compilation fails. E.An exception is thrown at runtime.
多项选择题 WhichtwoscenariosareNOTsafetoreplaceaStringBufferobjectwithaStringBuilderobject？（）
单项选择题 The variable df is an object of type DateFormat that has been initialized in line 11. What is the result if this code is run on December 14， 2000？（）
单项选择题 What is the result？（）
