cos(arcsin$\frac{1}{2}$)的值为（　　）

下列关于金刚石、石墨和C₆₀的说法正确的是（　　）

句型转换。（本题共5小题，每小题2分，共10分）

    Hello! Nice to meet you. Now let me introduce myself (自我介绍) to you. My name is Mary. I'm 12 years old. I'm from Canada and I speak English. I'm a tall girl. I have long brown hair and big blue eyes. I like music a lot. I often sing songs with my friends in my free time. I have a happy family. There are four people in my family. They are my mom, my dad, my sister and me. I like China very much and I want to visit Beijing, but I can't speak Chinese at all.

    I hope (希望) to be your friend, then we can help each other with English and Chinese.

根据材料内容，选择最佳答案。

例如，六年级(1)班有学生40人，其中有男生17人．男生人数占全班人数的几分之几？

一面红旗，长3米，宽2米．长是宽的几倍？宽是长的几分之几？

也可以说成：长与宽的比是____比____，宽与长的比是____比____．