牙釉质表面主要的无机物为（） A.铁和锌 B.钙和磷 C.镁和钠 D.氟和氯 E.碳 发布时间：2017-09-08 01:18 │ 来源：www.tikuol.com 题型：单项选择题 问题： 牙釉质表面主要的无机物为（）A.铁和锌B.钙和磷C.镁和钠D.氟和氯E.碳和磷酸钙矿物质
题型：单项选择题 从对话后的选项中选择适当的选项补全对话。Tony: Hi, Joy. Would you like to help to save the environment? Joy: 1_____ What can I do? Tony: Well, first, you can start by turning off the lights. Joy: Yes. That's easy. Sometimes I turn on the lights without thinking. What's next? Tony: Second, listen. 2_____ Don't take a bus or a taxi if you don't have to. Joy: That will save money, too. 3_____ Tony: 4_____ Joy: Mm, newspapers, magazines, mails … We get a lot of paper at home. Good idea. Tony: And last, take a bag when you go shopping. 5_____ Joy: OK. My parents do most of the shopping. I'll tell them. A. You can ride a bike. B. I don't know. C. Don't use plastic bags. D. What else? E. Try to recycle paper. 查看答案
题型：单项选择题 据锦州市环境监测部门公布的2006年6月7日空气质量日报，锦州市当日空气首要污染物为可吸入颗粒物，污染物指数为98．请你回答下列问题：（1）空气中可吸入颗粒物的主要来源有______（写出一种）；（2）空气中可吸入颗粒物造成的危害有______（写出一点）；（3）针对你说出的来源，提出一条减少空气中可吸入颗粒物的措施______． 查看答案
