题目

完形填空。 Have you ever planted a few trees on Tree Planting Day? Each year, millions of people, both old and young,  1  a lot of trees. But this may not be the best way to make your home a  2  place. Last week we visited a park in Hebei. We were  3  to find most of the trees had been burned. The workers told us that the trees  4  soon after they were planted because they weren’t watered well enough.  5  the workers burned them and cleaned the place for  6  trees to be planted this year.  7  a card found in one of the dead trees, a student wrote: “I hope this tr[2014·河北唐山]若直线y＝kx＋2k与圆x2＋y2＋mx＋4＝0至少有一个交点，则m的取值范围是________．