下图是“黄河流域简图”，图中表示黄土高原的数字代号是（     ）

阅读理解

    I have five children．I'm always busy when they're awake(醒着)．That's why I try to get up before everyone else．I get up at 5：00 am．The house is quiet．I drink a cup of coffee and read books．I love that time because it's mine and I can think without interruptions(打扰)．

    —Anna

    I'm a night person．I love the night．I feel sleepy all day and then at night I wake up(醒来)!I like to dance，watch movies or talk to friends at night.I never go to sleep before 2：00a.m.

    —James

    I'm a morning person．As soon as a little light comes through the window,I wake up and start my day．I try to do important work in the morning because I know that I think best at that time．After 1：00pm，I begin to slowdown!

    —Sandra

    I love tea time．I like to have tea in late afternoon．It's a time to stop the day's activities (活动)for an hour and talk with friends．Sometimes,people visit my home-then．Sometimes，I go to a friend's house for tea．

    —Bob

根据材料内容选择最佳答案。

在⊙O中，弦AB=8cm，弦心距OC=3cm，则该圆的半径为____ cm

按要求改写句子

赵琪琪在日记里写道：“马涛的学习成绩特别好，特别爱帮助别人，我有什么问题都喜欢问他，他也很高兴为我解答。但没过多久就有同学对我们指手画脚，说我们在谈恋爱。我很害怕，便从此躲着马涛，他也疏远了我。”这一事例说明（）
①男女同学之间应该群体交往，不能个别接触
②适度交往，男女同学可以互相影响，互相促进
③逃避不仅不能解决问题，反而会引起同学们更深的误会
④女同学与男同学自然、适度地交往是正常的