题目

 Allow children the space to express their opinions, ______they are different from your own.    A. as                     B. even though          C. until            D. as though 答案：B3．化简并求值：$\frac{{{a^2}-1}}{{{a^2}+6a+9}}$÷（a+1）×$\frac{{{a^2}-9}}{a-1}$，其中a=-1．