He ____ writing the paper now. He hadn’t written a single word when I left him ten minutes ago.

At last he       finish the work ahead of time.

       I’ve been working all day, but I feel as if I _______ nothing.

--- What have you learned from your experience in Japan? --- Well, meeting people from another culture ___ be very difficult.

—The research on the new bird flu virus vaccine is challenging and demanding. Who do you think can do the job?—____ my students have a try?