图是同学们常用的燕尾夹，AB=BC，当用力摁住C点打开该夹子时，可把____点看作支点，此时夹子可近似看作____杠杆（选填“省力”、“费力”或“等臂”）．

下列材料：

 东汉的《昌言》一书记载：“豪人之家，连栋数百，膏田满野，奴婢千群，徒附万计。”

请完成：

如图所示，一束光照射到平面镜上，请画出其反射光线．

在一定条件下，生态系统具有相对的稳定性。生态系统的稳定性是由于生态系统具有一定的____能力。组成生态系统的成分越____，其自我调节能力就越强。

阅读理解
B
    I went to Paris last August．I went there with my friend Jeff．We went by train．We stayed for five days in a small hotel in the center of Paris. The hotel was not expensive .Our room was OK—it was old，but very clean.
    In the mornings we visited all the famous tourist sights(著名的旅游景点)and museums．The Louvre Museum was my favorite ! We usually had some bread for lunch in a park．In the afternoons we walked around Paris．We took a lot of photos! And we had crepes! They were delicious! After a little sleep and a shower, in the evenings．We had dinner in small restaurants and then we went to pubs(酒吧)．We met very interesting people! We also made some good friends．
    We didn't buy any gifts．Everything was very expensive．But we sent(邮寄)very beautiful postcards(明信片)to our friends．We had a lot of fun ! It was an excellent holiday!
根据材料内容选择最佳答案。