题目

Did you know that if you need an alarm clock to wake up in the morning, you’re probably sleep-deprived （缺失）? ____36_______ . On average, American teens get two hours less than the average 9.2 hours of sleep they need each night to function at their best. There are many reasons why teens don’t get enough sleep. ____37_______ . When your parents were young, they might have read a book or watched television before trying to go to sleep. But today’s teens are likely to be surfing the Internet, texting, emailing, or playing video games right before bed. ____38_______ . And usi已知：如图，⊿ABC中，∠C=90°，AD是∠BAC的平分线，DE⊥AB于E,F在AC上，BD=DF,求证：CF=EB.