public class TestSeven extends Thread {  private static int x；  public synchronized void doThings（） {  int current = x；  current++；  x = current；  }  public void run（） {  doThings（）；  }  }  Which is true？（） 

• A、 Compilation fails.
• B、 An exception is thrown at runtime.
• C、 Synchronizing the run（） method would make the class thread-safe.
• D、 The data in variable “x” are protected from concurrent access problems.
• E、 Declaring the doThings（） method as static would make the class thread-safe.
• F、 Wrapping the statements within doThings（） in a synchronized（new Object（）） {} block would make the class thread-safe.