题目

The students here are friendly ______________ me. A . for B . to C . a D . about 答案：B7．由约束条件$\left\{\begin{array}{l}x，y≥0\\ y≤-3x+3\\ y≤kx+1\end{array}\right.$，确定的可行域D能被半径为$\frac{{\sqrt{2}}}{2}$的圆面完全覆盖，则实数k的取值范围是$（-∞，\frac{1}{3}]$．