题目

I’m Mary. I'm talking to you from the Hilltop School Skating Marathon. Here, students are skating to raise(募捐) money for charity(慈善). For every hour they skate, each student raises ten yuan for charity. The skating marathon has been going for five hours now, and several skaters are still skating. Alison was the first one to start and has been skating for the whole five hours. Next is Sam, and he has been skating for four hours. Lu Ning has been skating for four hours, too. And Li Chen just started an hour ago.【1】Why are the students skating?A.Because they want to know who is firs如图所示一束阳光与地面成30°角，试用一平面镜把阳光反射到竖直的井底．