public class Mycircle {  public double radius；  public double diameter；  public void setRadius（double radius）  this.radius = radius；  this.diameter= radius * 2；  }  public double getRadius（）   {  return radius；  }  Which statement is true？（）  

• A、 The Mycircle class is fully encapsulated.
• B、 The diameter of a given MyCircle is guaranteed to be twice its radius.
• C、 Lines 6 and 7 should be in a synchronized block to ensure encapsulation.
• D、 The radius of a MyCircle object can be set without affecting its diameter.