The main program creates three threads t1,t2, and t3. For the code below, which answer is valid? public static void main(String[ ] args) \{ t1.join0; t2. join0: 13.join0; System.out.println("End"): ) Thread t2 waits for t1 to finish. The output End waits for all threads to finish. All of them Thread t3 waits for t2 to finish. Thread t3 waits for t1 to finish