图2—2—9为普通光学显微镜结构示意图，请回答下列问题：

将一物块分成相等的A、B两部分靠在一起，下端放置在地面上，上端用绳子拴在天花板上，绳子处于竖直伸直状态，整个装置静止，则（   ）

    Every ____(秋天)I go to visit my grandparents．They live in the countryside．It takes me____(四十)minutes to get there by train．They have a big____(农场)．I always spend much time staying with different kinds of animals and____(植物)in it．From day to night，I have many____(有趣的) things to do．Sometimes，I climb trees and draw some pictures of beautiful flowers．Sometimes，my____(爷爷)and I feed the animals such as our dog，cows，chickens and ducks，He____(帮助)me know a lot about them．It is also great fun to see the little ____(黄色的)chickens eating noodles and ducks swimming in the river．In the countryside，I can____(学习)a lot from playing．I am never____(劳累的)of the days there．