题目

 ----- My son was admitted to a key university last year.    ----- Congratulations! His hard work finally ________,    A. paid for      B. paid off    C. paid back    D. paid attention 答案：B9．已知tanα=2，则$\frac{{{{sin}^3}α-2{{cos}^3}α}}{{sinα•{{cos}^2}α}}$的值为3．