在程序的下画线处应填入的选项是______。
public class Test______
public static void main(String args[])
Test t=new Test();
Tbread tt=new Thread(t);
tt.start();
public void run()
for(int i=0;i<5;i++)
System.out.println("i="+i);
A.implements Runnable
B.extends Thread
C.implements Thread
D.extends Runnable