具有“世界屋脊”之称的高原是（    ）

    If you're ever apart from your children， a new study says just talking on the phone will help just as much as a hug (拥抱).

    If you're a parent who spends long hours on the job， you probably feel sorry for spending so much time away from your kids. But the results of a new study show that a mother's voice alone can be just as comforting to an anxious child as physical contact (接触).

    In an experiment， researchers from the University of Wisconsin Madison asked a group of girls between the ages of 7 and 12 to solve math problems in front of judges — a stressful situation for anyone. Before the girls were set to give their answers， the researchers measured their levels of two hormones(荷尔蒙)：cortisol，which goes up during stressful periods， and oxytocin， the “love” hormone， which goes down at the same time.

    After the girls finished the problems， some of them got to meet up with their mothers right away. The moms came in and hugged the girls. Another group of the girls didn't see their mothers， but received phone calls from them， in which their mothers told them how well they'd done. The final group had no contact with their mothers， but instead watched an animal movie， March of the Penguins.

    Finally， the girls' hormone levels were measured again. Although the movie was interesting， it did nothing to reduce the children's anxiety—but， surprisingly， both the physical contact and phone calls from their mothers had the same effect on reducing the girls' stress levels.

    So， no matter how old you are， if you're feeling stressed about something in your life， a phone call to Mom might be just the key to help you feel better.

设函数f（x）=x²+ax+b，a，b∈R．

（1）若a+b=3，当x∈1，2时，f（x）≥0恒成立，求实数a的取值范围；

（2）是否存在实数对（a，b），使得不等式|f（x）|＞2在区间1，5上无解，若存在，试求出所有满足条件的实数对（a，b）；若不存在，请说明理由．

如果把分式$\frac{2x}{x-y}$中的x和y都扩大5倍，那么分式的值（　　）

害群之马

    黄帝将见^①大隗^②乎具茨^③之山，适遇牧马童子，问涂^④焉，曰：“若^⑤知具茨之山乎？”曰：“然^⑥。”“若知大隗之所存^⑦乎？”曰：“然。”黄帝曰：“异哉^⑧小童！非徒^⑨知具茨之山，又知大隗之所有。请问为天下^⑩”。小童辞^⑪。黄帝又问。小童曰：“夫为天下者，亦奚以异平牧马者哉^⑫？亦去其害马者而已矣。”黄帝再拜稽首^⑬，称天师而退。

（节选自《庄子·徐无鬼》）

【注】①见：拜访。②大隗：传说中的神名。③具茨：山名，在荥阳密县（今河南省密县）。④涂：同“途”，即路，⑤若：你。⑥然：是的。表应答。⑦所存：所在的地方。⑧异哉：了不起啊。异，不寻常。⑨非徒：不但，不只。⑩为天下：治理天下。⑪辞：谢绝。⑫亦奚以异乎牧马者哉：这与牧马还有什么两样吗；奚，何。以，因。异，不同。乎，于，相当于“与”、“跟”。⑬稽首：叩头。