题目

在蒸发皿中加热蒸干并灼烧下列物质的溶液，可以得到该物质固体的是(     ) A．氯化铝    B．碳酸氢钠     C．硫酸镁      D．高锰酸钾 答案：CTeens don’t understand the big fuss(小题大做).As the first generation to grow up in a wired world,they hardly know a time when computers weren’t around,and they eagerly catch the chance to spend hours online,chatting with friends.So what? But researchers nationwide are increasingly worried that teens are becoming isolated(孤寂),less skillful at person-to-person relationships,and perhaps numb(麻木) to the cheatings that are so much a part of the e-mail world.“And a teen’s sense of self and values may be changed in a world where personal connections can be limitless,”said Sherry Turkle. Another researcher,Robert Kraut,said he’s worried about the “opportunity costs”(机会成本) of so much online time for youths.He found that teens who used computers,even just a few hours a week,showed increased signs of loneliness and social isolation.“Chatting online may be better than watching television,but it’s worse than hanging out(闲逛) with real friends,”he said. Today’s teens,however,don’t see anything strange in the fact that the computer takes up a central place in their social lives.“School is busy and full of pressure.There’s almost no time to just hang out,”said Parker Rice,17.“Talking online is just catch-up time.” Teens say they feel good about what they say online or taking the time to think about a reply.Some teens admit that asking someone for a date,or breaking up,can be easier in message form,though they don’t want to do so.But they insist there’s no harm. The researchers argue that ______. A.teens may develop a different sense of values B.nothing is wrong with teens’ chatting online C.teens can manage their social connections D.spending hours online does much good to teens Teens think that talking online can help them ______. A.use computers properly B.improve their school work C.develop an interest in social skills D.reduce their mental pressures The text mainly deals with ______. A.teens’ pleasant online experience B.teens’ computer skills and school work C.the effects of the computer world on teens D.different opinions on teens’ chatting online The purpose of the text is to ______. A.describe computer research results B.draw attention to teens’ computer habits C.suggest ways to deal with problem teens D.discuss problems teens have at school