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.