完形填空

　　It started last fall when we had a beaver(海狸)move in the small stream beside our house．He immediately began taking down small trees, and soon our small stream 　　1　　 into a small pond．Every day he added more to his 　　2　　．

　　With his house built, we thought that would be the 　　3　　 of the beaver's busy activity as winter set in．　　4　　 to our surprise, he started chewing(咀嚼)on a 60-foot tall tree．We were 　　5　　 by the challenge this beaver was attempting．Over the 　　6　　, he would come out and chew a bit more．He had setbacks(挫折)as we faced 　　7　　 weather and major winter storms．We 　　8　　 thought that he would chew through this tree．But he kept coming back and would chew a bit more when the weather 　　9　　．

　　With spring finally arriving, we went down to see the beaver's 　　10　　 and the tree was going to come down soon!!Our beaver has now almost 　　11　　 chewed around and through the entire tree．

　　The beaver's original 　　12　　 was survival－to build a home for the winter．Working every day with that particular focus in mind, he 　　13　　 that goal at last．But the tree he 　　14　　 chewing on last fall was a future goal－he wanted the 　　15　　 to provide new food and branches to continue building his house the next year．Even with the setbacks he faced over the winter, he never 　　16　　．

　　Sharing our beaver's experience with you is to 　　17　　 you that sometimes we have a goal to just 　　18　　, but we also need to set goals for tomorrow．Sometimes, just surviving seems to occupy(占用)all of our 　　19　　－working every day, looking after our family, going to school, and so forth．But, if you do just a little bit when time allows, and keep 　　20　　 on your future goal, you will achieve it．