单项选择题

class ThreadBoth extends Thread implements Runnable { 
public void run(){ System.out.print("hi "); } 
public static void main(String [] args){ 
Thread t1 = new ThreadBoth();  
Thread t2 = new Thread(t1); 
t1.run(); 
t2.run(); 
} 
} 
结果为:() 

A.hi
B.hi hi
C.编译失败
D.代码运行,但无输出结果