题目

—It’s smoggy these days. That’s terrible! —Yes, I hope to plant trees. ______ trees, ______air pollution. A. The more; the fewer         B. the less; the more    C. The less; the fewer          D. The more; the less 答案：D17．抛物线y=$\frac{1}{2}$x2-kx+k与直线y=2x-1的两个交点距离最近时，k的取值为-1．