With two children _____ high school, the farmer couple have to work from morning till night.
154. Using renewable energy is a simple idea, but ______ we find it hard to put into practice.
155. In Beijing volunteers are making use of every minute to ______ their foreign languages because volunteers must pass a written test and an interview.
156. As is known to all, hard work will _____ in time.
157. The journey that _____ change Toby’s life started in July that year.
158. It is said in the book that Thomas Edison _____ the world leading inventor for about sixty years.