5. String foo = “base”； 
6. foo.substring（0，3）； 
7. foo.concat（“ket”） 
8.    
Type the value of foo at line 8.（）

A. An error at line 11 causes compilation to fail.
B. Errors at lines 7 and 8 cause compilation to fail.
C. The program prints pairs of values for x and y that might not always be the same on the same line （for example， “x=2， y=1”）
D. The program prints pairs of values for x and y that are always the same on the same line （for example， “x=1， y=1”. In addition， each value appears twice （for example， “x=1， y=1” followed by “x=1， y=1”）
E. The program prints pairs of values for x and y that are always the same on the same line （for example， “x=1， y=1”. In addition， each value appears twice （for example， “x=1， y=1” followed by “x=2s， y=2”）

A. Check（） can never return true.
B. Check（） can return true when setXY is called by multiple threads.
C. Check（） can return true when multiple threads call setX and setY separately.
D. Check（） can only return true if SyncTest is changed to allow x and y to be setseparately.

A. Extend java.lang.Thread and override the run method.
B. Extend java.lang.Runnable and override the start method.
C. Implement java.lang.thread and implement the run method.
D. Implement java.lang.Runnable and implement the run method.
E. Implement java.lang.Thread and implement the start method.