He broke his legs while ＿＿＿＿＿. 

(2013·安徽省名校联盟模拟)West of the city　　　, which provides a lot of job opportunities for the local people.

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

– Will you waste your time and money on that?   -- Certainly _______.

  Not until I dropped off from school ____ how much time I had wasted.