问题：

[单选]

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 + “>”；