秦岭﹣﹣淮河一线以北的主要植被类型是（　　）

椭圆满足这样的光学性质：从椭圆的一个焦点发射光线，经椭圆反射后，反射光线经过椭圆的另一个焦点．现在设有一个水平放置的椭圆形台球盘，满足方程：$\frac{X^2}{16}+\frac{y^2}{9}=1$，点A、B是它的两个焦点，当静止的小球放在点A处，从点A沿直线出发，经椭圆壁（非椭圆长轴端点）反弹后，回到点A时，小球经过的最短路程是（　　）

阅读下面材料，在空白处填入适当的内容（不多于3个词）或括号内单词的正确形式.

    This Christmas, maybe different from previous years, a strong desire drives me to make my own Christmas gifts. ____ (honest) speaking, I've promised myself this more than once. As ____ crafter (工匠), I've frequently thought I am ____ (suppose) to turn it into action. However, this year I really plan to stick ____ it. It's partly because I am short ____ money. More importantly, recently I ____ (return) from an inspiring trip around Britain, collecting some information about crafting for BBC's Newsnight.

    I was really struck by people's increasing ____ (enthusiastic) for making things. When I asked some people ____ they could sew(缝纫), only a few raised their hands. ____ when I asked who wanted to learn, nearly everyone responded positively, ____ (hope) to learn something practical.