—            are you late for school?

— Because I got up late.

将一张洋葱鳞片叶放在某一浓度的蔗糖溶液中，制成装片，放在显微镜下观察，有3种状态的细胞，如图所示，你认为这3个细胞在未发生上述情况之前，其细胞液的浓度依次是（　　）

——More and more students wear glasses in our school these days.——I agree with you. Students ___ keep on doing eye exercises to protect their eyes.

计算：﹣17+8=____