Given this method in a class：  public String toString（） {  StringBuffer buffer = new StringBuffer（）；  buffer.append（‟<‟）；  buffer.append（this.name）；  buffer.append（‟>‟）；  return buffer.toString（）；  }  Which is true？（） 

• A、 This code is NOT thread-safe.
• B、 The programmer can replace StringBuffer with StringBuilder with no other changes.
• C、 This code will perform well and converting the code to use StringBuilder will not enhance the performance.
• D、 This code will perform poorly. For better performance， the code should be rewritten： return “<“+ this.name + “>”；