单项选择题

请阅读下面程序
public class ExampleStringBuffer
public static void main (String[]args)
StringBuffer sb=new StringBuffer("test");
System.out.printIn("buffer="+sb);
System, out.printIn("length="+sb.length());


程序运行结果中在“length=”后输出的值是______。

A.10
B.4
C.20
D.30