给加下划线字注音，根据拼音写汉字
①襁褓____

② 拮据____ 
③ 根深dì固____

④ kè____ 尽职守

改革影响历史发展的进程。19世纪中期，世界历史上最典型的改革有俄国农奴制改革和日本明治维新。请结合所学知识回答问题。

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    Miss Lee is 21 years old. She likes students and her work. From Monday to Friday she stays at school and gives the students lessons. She has much work to do, but she often plays games with her students after school. On Sundays, she drives to her parents' home and stays with them. Sometimes she goes to see her friends on Sundays. She drives back to school on Monday morning. She's a good girl.

如图所示，质量为m的木块P在质量为M的长木板A上滑行，长木板放在水平地面上，一直处于静止状态。若长木板A与地面间的动摩擦因数为μ₁，木块P与长木板A间的动摩擦因数为μ₂，则长木板A受到地面的摩擦力大小为                  （   ）

下列实验操作正确的是（    ）