改革开放以来，中国净进口粮食占国内粮食生产的比重呈减少趋势，1978～1984年为3

观察下图，回答下列问题。

(1)把家兔的体腔分为胸腔和腹腔的结构是[ ]______，_________是哺乳动物所特有的。

(2)家兔的胸腔里所具有的结构是[ ]_______和[     ]________。

(3)与家兔呼吸有关的结构有[     ]_______和[ ]______。

(4)与家兔的消化有关的结构是[ ]_____、[     ]_______、[     ]______、[     ]______、[     ]_________。

如图所示，A是置于光滑水平面上的表面绝缘、质量m₁=1kg的小车，小车的左端放置有一个可视为质点的、质量m₂=2kg、电荷量q=+1×10^-4 C的小物块B，距小车右端s=2m处有一竖直的墙壁．小车所在空间有一个可以通过开关控制其有、无的水平向右的匀强电场，电场强度的大小为E=3×10⁴N/C．若小车A和小物块B一起由静止开始运动，且在小车与墙壁碰撞的瞬间撤去电场；碰撞时间忽略不计，碰撞过程无机械能的损失；小物块B始终未到达小车A的右端，它们之问的动摩擦因数μ=0.2，最大静摩擦力等于滑动摩擦力．小车不带电，g取10m/s²．求：

（1）有电场作用时小车A所受的摩擦力大小和方向？

（2）小车A第一次与墙壁相碰后向左运动的最远距离为多少？

（3）小车A第二次与墙壁相碰时的速度为多少？

（4）要使小物块B最终不滑离小车A，小车的长度至少多长？

（Alice advises Bill to read English every day and agrees to help him ．．．）

A：Why don ’t you look happy ？

B：Because I have a lot of trouble with my English, I can hardly pass the exam every time．   6   

A：Don ’t worry．   7     

B：No, I only read English before the exam．

A：Ah, that’s it. If you want to study it well，you must practise it every day．   8     

B：I’ll take your advice and try to practise reading English every day．  9     

A：All right. I’d like to. But in fact I still have some trouble with English, too．  10     

A．Will you help me with it？

B．Let’s help each other．

C．I’ll try my best to learn it well．

D．How do you like English？E．I really don ’t know what to do．

F．What are you going to do next？

G．Do you read English？

填入一个恰当的全对话，每空一词。

Liu Chang: What are you reading, Susan?

Susan: It's a postcard    1    my oldest friend.  Her name is Judy.  She lives in England now. I miss her.

           We often ate ice cream together after school.

Liu Chang: It's nice to    2    from old friends. You should send her a postcard from China.

Susan: I'll do that.

Liu Chang: I'm luckly. My oldest friend is my neighbor.

Susan:    3    did you meet your friend?

Liu Chang: I met him almost ten years ago. We    4    up together here in this town.

Susan: I guess you see him quite    5   .

Liu Chang: Not really. We're both very busy.  I see him about once a week.

群体思维