— Is Jack on duty today?
— It_______ be him. It's his turn tomorrow.
A：mustn't
B：won't
C：can't
如图所示，把同样大小的黑色棋子摆放在正多边形的边上，按照这样的规律摆下去，则第8个图形需要黑色棋子的个数是（ ）
猜一猜
一手拿着一个足球。____
两个孩子一起学习。____
