题目

如图所示实验，试管口木塞冲出过程中，下来说法正确的是A. 试管口出现的白雾是水蒸气B. 试管口出现白雾说明水蒸气内能增加C. 能量转化为机械能转化为内能D. 水蒸气对木塞做功，水蒸气的内能减少 答案：【答案】D【解析】A、试管口出现的白雾是水蒸气遇冷液化形成的小水珠，故A错误；B、白雾是水蒸气遇冷液化形成的，所以说明水蒸气内能减小，温度降低才会液化，故B错误；C、此过程的能量转化是内能转化为机械能，与内燃机的做功冲程类似，故C错误；D、当加热试管到一定程度时，水蒸气的内能阅读理解。      For one week in April, millions of people chose not to watch TV for “TV Turnoff Week”. TV Turnoff Week started in 1995 and is more popular every year. Many people discover that you can have a good timewith the TV off. If that sounds crazy to you, just have a look at some numbers:      ―An American teenager spends 900 hours every year at school; the same teenager spends 1,023 hoursevery year watching TV. That's 2 hours 49 minutes every day.      ―An average (平均) British person (not just teenagers) watches 3 hours 35 minutes every day.      ―In the US, most TV has adverts. American children see 20,000 adverts every year. By age 65, an American has seen two million ads!      But some research from Britain says that may not be a problem. The London Business School watched people carefully during TV adverts and they discovered that people don't watch a lot of the ads. Theresearchers discovered that the most common activity during the adverts was talking to other people in the room. Many other people started reading or doing housework or changed channels during adverts. They only really watched them about 25 percent of the time. 1. During TV Turnoff Week, many people don't _____. A. watch TV B. change channels C. watch adverts D. do their school work 2. From the passage we can learn that _____. A. American children see more adverts on TV than their parents B. British people spend more than 3 hours a day in front of their TV C. Researchers noticed that most people changed channels during ads D. An American teenager spends more time at school than watching TV 3. The writer's purpose is _____. A. to advise us to spend less time on TVB. to tell us how to avoid watching adverts C. to show us how many adverts American TV has D. to ask us to turn off TV during TV Turnoff Week