The results of the medical checkup suggested that my father ______ in poor health, so the doctor suggested that he ______ smoking and take more exercise.

--- It is strange that he ______ come so late. --- Something unexpected must have happened to him.

________ more careful, his ship would not have sunk. 

—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?

More and more people have come to realize that if we had taken effective measures much earlier, the air quality ______ so seriously now.