如图所示，两个质量均为m的小环套在一水平放置的粗糙长杆上，两根长度均为l的轻绳一端系在小环上，另一端系在质量为M的木块上，两个小环之间的距离也为l，小环保持静止．（认为最大静摩擦力等于滑动摩擦力）．试求：

下列关于神经元的叙述，不正确的是（  ）

计算（－2$\frac{1}{2}$）×（－3$\frac{1}{3}$）×（－1）的结果是（   ）

阅读理解

Dear Liz，

Thank you for your great present．I had a successful birthday party last Saturday.Ten of classmates came to my home．Well,we played games,danced to music and enjoyed delicious food．We shared a big cake with a small chocolate monkey．My mum bought the cake．Miss Smith was a special guest(客人)．She happened to meet my mufti in the cake shop near my home．She also joined us and drew a picture for me．I was happy to receive many kinds of presents，such as cards．balls and CDs．Your book about animals was the best．You know,I like animals and dogs are my favourite．There is a small black cat in my grandparents' home．I'd like to play with—it when I visit my grandparents once a week．It's cold today．What's the weather like in your village? Let's go to the new library when you come back．

Yours，

Elizabeth

根据材料内容选择最佳答案。