题干

自行车是我们熟悉的交通工具,从自行车的结构和使用来看,它涉及到不少的有关摩擦的知识,

例如:A轮胎上有花纹 

B车轮做成圆形 

C塑料套紧紧套在车把上 

D在转动部分加润滑油

E脚踏板凹凸不平  

F刹车时用力捏闸  

G车轴处装有滚珠  

H车把上有凹槽。
上述各项内容中,属于通过改变接触面的粗糙程度而增大摩擦的是____ ;通过变滑动为滚动而减小摩擦的是____ 。(只填写各选项的字母)

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AEH,BG

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    It's the holiday season, the time when we connect with family and friends. Social media sites like Twitter and Facebook are full of festive pictures, featuring parents' catching and sharing those special family moments, their child's wish list, and maybe even a cute video of their child dancing to “Jingle Bell Rock” while wearing a diaper (尿片) and Santa hat. Swelling with pride, parents can't wait to get approval with a “thumbs up” or better yet a personalized message on their treasured post.

    Adults should be able to post what they want online. However, when exposing family moments online, are they sharing too much information? Do parents have the right to share those cute now, but embarrassing later moments about kids? Have children willingly given their agreement to sharing their cute but funny video online?

    A recent study found that 75% of parents turn to social media for parenting-related information and social support. There is even a term used to describe the overuse of sharing too much information about kids on social media: “sharenting”. Research also finds that “sharenting” isn't going anywhere anytime soon. What's troublesome is that a typical parent has about 150 Facebook friends and only a third of them are actual friends. So that brings up good questions – Who are we really sharing our information with and why? Who knows when and where that photo could resurface in the future?

    While there's no reliable information on how young children feel about things posted online, we do have information about how teens feel. According to a report by the Family Online Safety Institute, 76% of teens are concerned about their privacy. Many teens constantly search for new apps that allow anonymity. When names are required, they use screen names that don't reveal real information. If our teens are doing a better job of protecting themselves online, shouldn't parents take the lead and do the same? Plus, with more and more college admission representatives and potential employers surfing the internet for potential candidates, we'd hate for one of our posts to change an important decision. Think about it … online reputations are now becoming inseparable with real life ones.

    Of course, we can secure our privacy settings, only allowing our friends to view pictures, posts and videos, but that doesn't stop others from uploading our pictures. Adults need to be cautious of sharing information online, especially information about children.

    So, this holiday season, enjoy family time and share those special memories with family and friends. Before clicking the app to upload photos or videos, stop and think twice.