—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?

—What does the sign over there read?—No person        smoke or carry a lighted cigarette, cigar or pipe in this area.

Walking exercises ____ be boring at times, but on a clear sunny morning nothing could be better．

(2014·山东省实验中学一模)You________get an all­expense­paid vacation to Australia if you can answer all the questions.

--______you swim? -- No, I can’t.