设函数f（x）=$\left\{\begin{array}{c}2x-1,x<1\\ \frac{1}{x},x\ge 1\end{array}\right.$则f（f（2））=（　　）

    Little Red Riding Hood lives near a forest (森林). She often goes to visit her grandma. She usually brings her some food. One day, when she is on her way to her grandma's home, a wolf sees her. The wolf stops her and asks, “Where are you going?” “My grandma's home.” answers Little Red Riding Hood. The wolf suggests (建议）picking some flowers for her grandma. The wolf runs to her grandma's home first. He eats the grandma. He is lying (躺）in the grandma's bed. Little Red Riding Hood comes and the wolf wants to eat her. Little Red Riding Hood cries for help. A hunter (猎人）comes quickly. The wolf is afraid, and he runs away.

如图所示，质量为m的小球从距离地面高H的A点由静止开始释放，落到地面上后又陷入泥潭中，由于受到阻力作用到达距地面深度为h的B点速度减为零．不计空气阻力，重力加速度为g．关于小球下落的整个过程，下列说法中不正确的是（   ）

①氯气与氢氧化钠溶液反应生成次氯酸盐（ClO^﹣）：____．

②次氯酸盐氧化氰化物（CN^﹣）生成氰酸盐（CNO^﹣）：ClO^﹣+CN^﹣=CNO^﹣+2Cl^﹣

③过量的次氯酸盐在碱性溶液中氧化氰酸盐生成CO₃^2﹣和N₂：____．

如图所示，粗略测量小明同学引体向上运动的功率时，下列物理量不需要测量的是（　　）