阅读课文《一幅名扬中外的画》

      画上的街市可热闹了。街上有挂着各种招牌的店铺、作坊、酒楼、茶馆……走在街上的，是来来往往、形态各异的人：有的骑着马，有的挑着担，有的赶着毛驴，有的推着独轮车，有的悠闲地在街上溜达。画面上的这些人，有的不到一寸，有的甚至只有黄豆那么大。别看画上的人小，每个人在干什么，都能看得清清楚楚。

已知实数x，y满足$\left\{\begin{array}{c}y\ge 1\\ y\le 2x-1\\ x+y\le 8\end{array}\right.$，则目标函数z=x﹣y的最小值为（　　）

    Are you facing a situation that looks impossible to fix?

    In 1969,the pollution was terrible along the Cuyahoga River Cleveland, Ohio. It____(be) unimaginable that it could ever be cleaned up. The river was so polluted that it____(actual) caught fire and burned. Now, years later, this river is one of____most outstanding（杰出的）examples of environmental cleanup.

    But the river wasn't changed in a few days____even a few months. It took years of work ____(reduce) the industrial pollution and clean the water. Finally, that hard work paid off and now the water in the river is____(clean) than ever.

    Maybe you are facing an impossible situation. Maybe you leave a habit____is driving your family crazy. Possibly you drink too much or don't know how to control your credit card use. When you face such an impossible situation, don't you want a quick fix and something to change immediately?

    While there are____(amaze) stories of instant transformation, for most of us the____(change) are gradual and require a lot of effort and work, like cleaning up a polluted river. Just be ____(patience).