用所给词的适当形式填空

①We don't have any ____ (lesson) on Sundays.

②The teacher is very busy. He often  ____ (sleep) at half past eleven.

③ I can ____ (play) football, but Burt can't.

④What____ he usually ____ (do) after school?

⑤ You can't go to bed until (直到) you finish ____ (do) your homework.

125×16=____

已知函数f（x）满足f（x）=x²﹣2（a+2）x+a²，g（x）=﹣x²+2（a﹣2）x﹣a²+8．设H₁（x）=max{f（x），g（x）}，H₂（x）=min{f（x），g（x）}（max（p，q）表示p，q中的较大值，min（p，q）表示p，q中的较小值），记H₁（x）的最小值为A，H₂（x）的最大值为B，则A﹣B=（　　）

 如图所示，一个小球静止于水平地面上，请你在图中画出小球受到的重力和支持力的示意图

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