问题：

[单选]

public class SyncTest { 
private int x； 
private int y； 
private synchronized void setX（ int i ） { x = i； } 
private synchronized void setY（ int i ） { y = i； } 
public void setXY（ int i ） { setX（i）； setY（i）； } 
public synchronized boolean check（） { return x != y； } 
}  
Under which condition will check return true when called from a different class？ （） 

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 return true only if SyncTest is changed to allow x and y to be set separately.