对于实数a，b，现用“☆”定义新运算：a☆b＝a³－ab，那么将多项式a☆4因式分解，其结果为(       )

阅读理解
A
    My name's Li Yan．I'm from Belling and I'm 13 years old.I study in No．1 Middle School．I'm in Class 2．Grade 7．I'm in the school music club．I can play the guitar well and I am good at playing the piano．Lang Lang is my favorite musician．I dream of being a musician like him．
    LiYue is my sister．We are twins(双胞胎)．We go to the same school， but she is in Class 4．Grade 7．She can play ping-pong very well and she is in the sports club．She likes Zhang Jike and Ma Long best．She often watches them play ping-pong on TV.
    My sister and I are learning how to swim．We are not good at it now,but we are trying our best(尽我们最大的努力)to learn it．It is a really healthy sport．
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已知多项式 $\left(x^2-mx+1\right)\left(x-2\right)$ 的积中不含x²项，则m的值是 (      )

抛物线 $y=\frac{1}{4}{x}^2$ 的准线方程是（   ）

某工厂一蓄水池有漏水现象，如果用一台水泵向该水池注水，需用8小时才能将空水池注满，如果用同样的两台水泵向该水池注水，只需3.2小时就能将空池注满，如要求2小时内就将该水池注满，至少需要几台这样的水泵？