阅读下列短文，从短文后各题所给的A,B,C,D四个选项中，选出最佳选项

     Last fall a beaver moved into the small stream beside our house. He began taking down small trees right away. and in a couple of weeks our stream turned into a pond(水塘).Every day,he added more to his dam(水坝)and to his house. We're sure you've all heard the saying, "as busy as a beaver". Now, we understand this saying as we saw the work that this beaver did over a very short period of time.

    We thought that would be the last of the beaver's busy activity as winter came. To our amazement, however, he started chewing(咀嚼)on a very large tree. The tree was over 18 meters tall and around 1.5 meters in diameter(直径).We were amazed at the challenge this beaver was trying. All winter, he chewed and chewed. He had setbacks(挫折)as we faced major winter storms and ice-cold weather. But sure enough, when the weather allowed, he would come back and chew a bit more.

    The beaver's first goal(目标)was to survive--to build home for the winter. Working every day with that goal in mind, he successfully achieved that goal. But the large tree he started chewing on last fall was a future goal一he wanted the large tree to provide new food and branches(树枝)for the coming spring. Even with the setbacks he faced over the winter, he never gave up until he reached it.

   Our beaver's experience reminds us that we need to set goals for tomorrow. Sometimes just surviving seems to take up all of our time.  But, if you do just a little bit when time allows and stick to your future goal, you will achieve it.

    When faced with setbacks, have your goal in heart and don't let the setbacks stop you. Keep chewing like the beaver, and you will achieve your goal in the end.