题干

下列函数中,自变量的取值范围选取错误的是(  )

A:y=2x2中,x取全体实数

B:y=1x+1中,x取x≠-1的实数

C:y=x-2中,x取x≥2的实数

D:y=1x+3中,x取x≥-3的实数

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答案(点此获取答案解析)

D

同类题1

完形填空

    It was one of the hottest days of the dry season. We had not seen rain 1almost a month. The crops were dying. If we 2see some rain soon, we would lose everything

    I was making lunch in the kitchen when I saw my3 son, Billy, walking towards the woods. He was walking with a great effort... trying to be as still as possible. Minutes later, he was once again walking towards the woods. I 4 stand it any longer. I went out of the house and followed him.He was cupping both hands in front of him as he walked, being very careful not to spill (溢出)the water he carried.As I came closer, I saw5 sight. Several large deer stood in front of him. Billy walked straight up to them. I almost screamed for him to get away. But the deer 6 hurt him nor even moved as Billy got down. And then I saw a baby deer7 on the ground, thirsty, lift its head to lap up(舔) the water in my boy's hands. When the water was gone, Billy jumped up to run back to the house. I followed him back to a tap. Billy opened it and let the drip slowly fill up his "cup".8he stood up and began to turn back, I was there in front of him. His little eyes9 with tears. Very quickly, he explained 10he was not wasting water. The week before, he had made 11 same trouble with our horses,12 caused him a lecture from his father about the importance of not wasting water.

    This time, I joined him, with a small pot of water from the kitchen. I let him 13 the baby deer alone , for it was 14job. As the tears that rolled down my face began to hit the ground, they15by other drops... more drops... and more. I looked up at the sky. All I can say is that the rain came that day saved our farm, just like the actions of one little boy saved the little deer.

同类题4

阅读下文,回答问题

拔掉心底的篱笆

       我小时候学习成绩不错,但不知从哪儿听来的;一个人如果学习成绩优秀,那么他在体育方面多半会很差。另外,我常常感冒,这让我更加确信我是个体质弱的人,不适合竞技类的运动项目。

       有一次学校举办运动会,我很想报名田径比赛,但你知道,我是不会报的。

       那天体育老师找到我:你怎么没报项目?我把心底的担忧倒了出来。体育老师的话,刷新了我小时候的“常识”:你错了,人都会感冒,不时地感冒一次,恰恰证明你的免疫系统是敏感且运转正常的,反倒可能说明你体质好;跑步是可以练出来的,也许你在耐劳方面出色,来试试吧!

       你完全能想象当时有多高兴,猛然发现自己的先天条件并无缺陷,甚至有优势,那些被我看得比山还重的束缚,仅仅是因为过去的我孤陋寡闻。

       我最终报名参加了长度最长的长跑比赛,拿了第三名。

       高中二时,学校文理分科。从小到大,我的数学成绩没有语文成绩好,虽然也不低,师长们多年来在耳边不停提醒我:你数学需要提高啊!你偏科啦!我渐渐也承认了这个现实:我脑子不灵,于是我报了文科班,但依旧对数学这一科怕得要死。分科之后,教我们数学的是当地名声赫赫的泰斗级老师。

       有一次他问我:你成绩那么好?为什么不把数学也兼顾一下呢?我说:老师,我从小数学就偏科,我不擅长学数学。

       他接下来的一番话刷新了我读高中时的“常识”:你错了,咱们现在学的内容跟以前的知识并没太大联系,从前学得不好,现在可能学得好;你刚刚的表达不准确,什么叫“我不擅长数学”?数学领域分为代数、几何,等好多部分,涉及的能力有人的空间想象能力、逻辑思维能力等,我看你的逻辑能力就很强,可能擅长数学中的一部分。

        我听到这话别提多高兴,感觉整个人都解放了:原来,“科学表明”,我在数学领域不但不是废物,而且非常“有戏”。那学期的考试,数学满分值150.我拿了142分。

       参加工作后,一位读者朋友过了不惑之年,想学外语,但恐于年龄大学不成,问我怎么办。说实话,我没法盲目地激励他。众所周知,人岁数一大,大脑会退化。后来,我偶然看到这样一则消息:最新研究结果显示,中老年人计算速度及注意力方面确实下降了,但脑细胞丝毫没减少,在模式识别、逻辑推理方面不降反增,年纪大了也不存在“舌头变硬学发音会吃力”这一说。我赶紧把这喜讯告诉他,他像我小时候一样欢喜,如今已经学有小成了。

       人的和你多恐惧和心理障碍,都是自己强加给自己的,抑或是早年间被别人在脑海里围起来的篱笆。你经历得越多,知道得越多,就越有可能发现很多自己以前觉得是问题的地方其实都是不问题。另一个方面,可能这世上从来就不存在什么难以逾越的篱笆,有时候,脚下的障碍其实是一排娇弱的花。

(摘自《青年文摘》有删改)