1.STDIN_FILENO = 0, STDOUT_FILENO = 1, STDERR_FILENO = 2
2.STDOUT_FILENO = 0, STDERR_FILENO = 1, STDERR_FILENO = 2
3.STDERR_FILENO = 0, STDOUT_FILENO = 1, STDIN_FILENO = 2
4.STDIN_FILENO = 0, STDERR_FILENO = 1, STDOUT_FILENO = 2
Answer:2