Keep up a good state of mind even if you _____ fail plenty of times.

-- Could I invite my friends to my birthday party?   -- Sorry, you _________.

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

It’s quite warm here; we __________turn the heating on yet.

一Shall we meet at the station at 8 am?—In fact, we _______. The train _______ until l0 a.m.