A:6a cm2
B:(6a+9)cm2
C:(6a﹣9)cm2
D:(a2﹣6a+9)cm2
They won't study abroad ____ they ____ high school.
给下面句子加上标点符号。
她想____父亲年老多病____难以出征____弟弟又小____还不够当兵的年龄____自己理应为国为家分忧____