题目

 Thank you for all your hard work last week. I don’t think we _____ it without you. A. can manage                       B. could have managed C. could manage                      D. can have managed   答案：B19．先化简，再求值：$\frac{{a}^{2}+ab}{{a}^{2}+2ab+{b}^{2}}$-（a-b）÷$\frac{{a}^{2}-{b}^{2}}{b}$，其中a=2+$\sqrt{2}$，b=2-$\sqrt{2}$．