The experiment shows that proper amounts of exercise, if      regularly,  can improve our health.   

Only when one leaves his homeland ______ how much he loves his motherland.

These problems, __________, will seriously affect the growth of teenagers and even the nation’s future.    

Only when he got on the train _________ that he had left his mobile phone at home．

I was told that _________ somebody to meet me at the station but _________ anybody.

While ____ the dog, you should take care not to get loose . Otherwise, it may be dangerous to strangers.

—My sister took a photo with Jay Chou last year.
—______.

Only when I made it to the train station _______ that I had left my ticket at home.

Only by practising constantly__________ greater progress.

________ entered the classroom _________ the bell rang.