题目

In 1974, when I was 18,1 took up hang-gliding and paragliding. Today Tm a professional hang-glide instructor, but at the time I was one of only about a dozen in the country doing it. I was lucky to survive: the sport was so new and dangerous then. In 1997 I heard about the Birdman competition, in which participants (参与者）compete to fly the furthest distance; I thought it sounded like fun. I felt that a hang-glider, which usually travels around 90 metres, could go as far as 100 metres one day. The first leap was frightening: a huge crosswind meant I had to take off at almost 90 d17、去年我国部分地区突发的“非典型肺炎威胁着人们的身体健康．过氧乙酸可以起到消毒作用，其分子结构如示意图所示（注：-表示碳原子；-表示氧原子；-表示氢原子）．根据分子结构图回答下列问题：过氧乙酸由3种元素组成，化学式可写为C2H4O3，相对分子质量是76．