如图是酒精测试仪的原理图，R₀为定值电阻。已知酒精气体传感器的电阻与酒精气体的浓度成反比，如果测试到的酒精气体浓度越大，你们认为正确的是（　 　）

水葫芦的引进使我国云南滇池原有的水生生物几乎绝迹，使当地的生物多样性受到极大的威胁，这种现象叫 (    )                                                      

控制变量是科学探究的重要方法之一．小华同学实验中发现：把质量相等的不同物质放入同样一杯水中，有的溶解快，有的溶解多，有的溶解又快又多．是哪些因素影响着物质溶解的快慢与多少呢？

请你参考下表硝酸钾的溶解度随温度的变化关系，以硝酸钾为例，选择一种可能影响硝酸钾溶解快慢的因素设计实验进行探究：

①影响因素：____ 实验中，控制不变的因素是____ ．

②实验方案：____ ．

完型填空

Jerry is the kind of guy you love to work and live with. He is always happy and always has something 1  to say. When someone asks him how he is doing, he must reply, “If I   2 any better, I would be twins! ”

Jerry is an 3 manager because he has several waiters who have followed him around from restaurant to restaurant. The reason the waiters follow him is his 4 to life. He always  5 others. If a waiter is having a bad day, Jerry is there telling the waiter how to  6the positive side of the situation.

I was very curious(好奇的) about his positive attitude, 7one day I went up to Jerry and asked him, “I don’t get it! You are a positive person 8. How do you do it? ”

Jerry replied, “Each morning I 9  and say to myself, ‘Jerry, you have two choices(选择) today. You can choose to be happy or you can choose to be unhappy. ’I choose to be happy. Each time something bad happens, I can choose to be a victim (牺牲品)or I can choose to learn from it. I choose to learn from it. ”

Life is all about choices. Please remember: “You are what you  10  . ”