浙江省卫生厅2014年2月12日通报，浙江省新增3例人感染H7N9禽流感病例，2014开年至今H7N9禽流感已经袭击了84人。

（1）从传染病学分析，H7N9禽流感病毒属于____ ．从组成上看，病毒一般都由蛋白质外壳和____ 内部的组成。

（2）现有研究结果表明，普通的流感疫苗对预防H7N9禽流感没有明显效果．这说明普通流感疫苗不能使人产生抵抗H7N9禽流感病毒的____ ，因而不能获得对H7N9禽流感的抵抗力．从免疫学的角度看，给人体接种的疫苗属于____ 。

（3）人感染H7N9后会出现发烧症状引起食欲降低，其原因是____ 。

（4）为了防止H7N9禽流感的蔓延，专家建议：

①出现发热、咳嗽等流感症状，及时就医。

②吃禽肉要煮熟煮透，不吃生鸡蛋、半生煎蛋，带血白斩鸡。

③勤洗手，室内勤通风。

④一旦发现禽流感感染的家禽立即灭杀．以上措施中，一定不属于控制传染源的是____ 。

元素X的氧化物中，X元素与氧元素的质量比为7:20，X元素与氧元素的相对原子质量之比为7:8。该化合物化学式为（　）

    When Henry came home from the office last Thursday night, he saw a note from his wife on the kitchen table. "Henry, "the note said, "my mother isn't well and I am going home to be with her for a few days. There are a few things that ought to be done while I am away. First, would you please stop at the shoe repairman's and get my brown shoes? And go to the supermarket and get some coffee, milk and butter. When you get home, please telephone Mary and tell her I won't be able to go to her party tomorrow evening. Tell her why I can't come. There are three things that must be done before you go to work tomorrow morning：Leave a note for the milkman asking for just one quart of milk, not two; put the garbage in the backyard; give the dog something to eat. On Saturday, cut the grass in the backyard. The newspaper boy will come on Saturday afternoon. Be sure to give him money. ”

一个圆形水池的半径是20米，绕这个水池走一圈，要走多少米？（保留两位小数）