请阅读下面程序
public class ThreadTest
public static vodi main(Sting args[])
Thread t1=new Thread(new Hello());
Thread t2=new Thread(new Hello());
t1.start();
t2.start();
class Hello implements Runnable
int i;
public void run()
while (true)
System.out.printIn("Hello"+i++);
if(i==5) break;
该程序创建线程使用的方法是______。
A．继承Thread类
B．实现Runnable接口
C．t1.start()
D．t2.start()
