题干

有关我国各民族的地区分布状况的叙述,正确的是(  )

A:汉族全部分布在东部

B:少数民族全部分布在西部

C:各民族均匀分布

D:我国各民族总的分布特点是大散居,小聚居,交错杂居

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答案(点此获取答案解析)

D

同类题3

科谱阅读理解。

人的大脑概括来说有五方面的功能:感觉、控制运动、记忆、情感和情绪、认知(认知包括逻辑思维、判断、计划和决策等)。

灵长类进化到人,大脑容量增加了一倍,主要是大脑前额叶越来越大。那么这部分区域到底起什么作用呢?这里先讲一个小故事。有一个人对神经科学有巨大的贡献,那就是盖奇。在一次意外事故中,他的脸颊部分被一根铁钎穿过,恰好损毁了他的大脑前额叶。但他却奇迹般地活了下来,感觉功能和运动功能没有问题,对发生事故以前经历过的事情也记忆犹新。然而,时间久了,医生发现他已经完全变了一个人:他对事物的判断和解能力已完全不能像正常人那样。经过长时间的研究,确认前额叶的基本功能是负责工作记忆。工作记忆是一种对信息进行短暂储存和加工以指导下一步行动的记忆,这种记忆的信息就像存在电脑内存里的信息数据。

如图是说明工作记忆的简单实验:猴子关在笼子里,笼子外左右各有一个托盘,左边托盘里放上一颗葡萄干,然后将葡萄干用布遮上,再把笼子外的帘子拉下。经过几秒到十几秒,再把帘子拉开,这时猴子会毫不犹豫地选择从左边托盘中将葡萄干拿过来吃。这个实验说明猴子有一种短暂的记忆功能,那就是工作记忆。之前看到“左边托盘有葡萄干”的信息已经在猴子前额叶中进行了储存和处理,等帘子拉开,就会指导它去取葡萄干。

经过一系列实验可以总结出三点:首先,前额叶是一个非常重要的行使工作记忆的脑结构,如果损伤了,简单的工作记忆的功能就不能完成。其次,信息在前额叶不但被储存,还有加工过程,从而使得猴子可以做出后面的行为。第三,信息加工过程是通过前额叶里某些神经元延迟性的持续放电完成的。

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同类题4

阅读下面短文,掌握其大意,然后从36—55各题所给的四个选项(A、B、C和D)中,选出最佳选项,并在答题卡上将该项涂黑。

    Every day, I drive home along Colorado Blvd, a wide street with four lanes on each side of the median (中央分隔带护栏). I always notice a homeless man standing on the corner of Colorado Blvd, 1 for spare change with a sign in his hand.
Last Monday, when I was 2 him, he suddenly threw down his sign and rushed into the middle of the street. At this time I 3 a car moving across the 3 lanes of traffic and heading for the  median. The 4 man ran to the side of the car and attempted to push the car back in the right 5. He also knocked on the window of the vehicle, but all  6 Immediately, he ran across the small median into four lanes of oncoming traffic, 7 madly for the cars to stop. Thankfully, all speeding cars 8 to stop just in time to 9 hitting him. The car which was out of 10 came Moving across the median and the four lanes of traffic, where just seconds ago cars had been traveling with 11 speeds.
    The homeless man jumped back in front of the 12 to attempt slowing it down again. By this time, we were able to 13 and help the man stop the car 14 it ran into a supermarket on the other side of the road. As it 15 out, the woman driver had a heart attack while driving and became 16 in the front seat.
    The homeless man is indeed a hero. He spends every day getting 17 by people who are trying not to make 18 contact with him so that they don't feel bad not giving him money. Yet he didn't  even hesitate to risk his life to save this lady and other drivers who would have 19 into her. He didn't think of his safety, nor did he expect anything in return. Heroes do exist in the most 20 places.