Given a class Repetition:
Which code should be inserted at line 1 of Demo.java to compile and run Demo to print "pizzapizza"?（）

单项选择题Given: Which code fragment, inserted at line 23, allows the code to compile?（）

A.df = new DateFormat();
B.df = Date.getFormat();
C.df = date.getFormat();
D.df = DateFormat.getFormat();
E.df = DateFormat.getInstance();

单项选择题Given: Which regular expression, inserted at line 12, correctly splits test into Test A , Test B , and Test C ?（）

A.String regex=""；
B.String regex=" ."；
C.String regex=".*"；
D.String regex="\\s"；
E.String regex="\\.\\s*"；
F.String regex="\\w[\.]+"；

单项选择题Given: What is the result when the programmer attempts to compile the code and run it with the command java Converter 12?（）

A.It is true that j==i.
B.It is false that j==i.
C.An exception is thrown at runtime.
D.Compilation fails because of an error in line 13.

单项选择题Given that the current directory is empty, and that the user has read and write permissions, and the following: Which statement is true?（）

A.Compilation fails.
B.The file system has a new empty directory named dir.
C.The file system has a new empty directory named newDir.
D.The file system has a directory named dir, containing a file f1.txt.
E.The file system has a directory named newDir, containing a file f1.txt.

单项选择题Given: Which code fragment, inserted at line 24, outputs 123abc 123abc ?（）

A.sb1.append("abc"); s1.append("abc");
B.sb1.append("abc"); s1.concat("abc");
C.sb1.concat("abc"); s1.append("abc");
D.sb1.concat("abc"); s1.concat("abc");
E.sb1.append("abc"); s1 = s1.concat("abc");
F.sb1.concat("abc"); s1 = s1.concat("abc");
G.sb1.append("abc"); s1 = s1 + s1.concat("abc");
H.sb1.concat("abc"); s1 = s1 + s1.concat("abc");