最近，你班围绕“汉字文化”开展了“集体视听”系列活动。

（1）画线段AC=30mm（点A在左侧）；

（2）以C为顶点，CA为一边，画∠ACM=90°；

（3）以A为顶点，AC为一边，在∠ACM的同侧画∠CAN=60°，AN与CM相交于点B；量得AB是多少mm？

（4）画出AB中点D，连接DC，此时量得DC是多少mm？请你猜想AB与DC的数量关系是：AB是DC的多少倍？

（5）作点D到直线BC的距离DE，且量得DE等于多少mm？请你猜想DE与AC的数量关系是：DE和AC的数量关系是？，位置关系是？．

    You may know about “junk food” like French fries.But do you know about “junk sleep”？

    Recently, a British survey found that electronic(电子的) products in teenagers' bedrooms are affecting(影响) their sleep.

    The survey was done among 1，000 British kids from 12 to 16.It found that 30% of them got just 4 to 7 hours of sleep every day.But doctors say they need 8 to 9 hours.

    Almost a quarter of the kids said they fell asleep more than once a week while watching TV, listening to music or using other electronic products.

    “This is very worrying，” said Dr.Chris Idzikowski，a British expert，“We call it 'junk sleep'．It means you don't get enough sleep and the quality of the sleep is bad, too.If you don't get a good rest，you don't perform well in school the next day.”

    The survey found that 40% of the kids felt tired each day，with girls between 13 and 16 feeling the worst.Nearly all the teenagers have a cellphone，an iPad or a TV in their bedrooms.And many of them have all the three.