Hi! I'm Linda. I am ____ English girl. Now I'm in Shanghai with my parents. There is a ____ store next to my house. ____ name is Xingxing Clothes Store. You can buy all kinds of ____ in it. They have sweaters at a very good ____. Do you need bags? They ____ great bags for 26yuan each. They have hats ____ red, black and yellow. They ____ have nice skirts for girls. For ____, they have shorts and sports socks. Do you ____ to come here? Let's have a look this afternoon.

一质点做速度逐渐增大的匀加速直线运动，在时间间隔t内位移为s，动能变为原来的9倍，该质点的加速度为（   ）