题干

在如图所示的电路中,闭合开关S后会发现与弹簧相连的条形磁体(颜色深的一极为N极)向左滑动.则下列分析正确的是(   )

A:电磁铁的A端为N极,电源左端为“+”极

B:利用这一现象所揭示的原理可制成的设备是发电机

C:当滑动变阻器的滑动片P向左端移动时,弹簧将伸长

D:若滑动变阻器的滑片P不动,抽去电磁铁铁芯,弹簧将变长

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A

同类题1

我国粮食产业发展的紧迫形势说明粮食生产的供给侧改革已迫在眉睫。阅读材料,回答下列问题。

材料一:粮食多了。近年来我国实现了粮食产量、库存和进口“三量齐增”。尽管粮食连年丰收,但由于分散化、粗放式的生产等原因,使国内粮食产品缺乏价格竞争力,导致国内粮食进仓库、进口粮食进市场。为避免谷贱伤农、保护农民种粮积极性而建立起的国家粮食收储政策,因粮食供给总量的不断攀升而压力加大,使政府财政负担加重。

    粮食缺了。一方面,国内中低端粮食产品相对过剩、同质化恶性竞争不断加剧,而深加工、高品质、安全的农产品供给却显不足;另一方面,粮食品种的供需矛盾也比较突出,小麦已4年产不足需、大豆对外依存度则高达80%。

    未来,随着人口增加和工业化、城镇化的推进,粮食消费需求将保持刚性增长,而我国资源环境的“硬约束”将使粮食生产继续维持稳定增长的难度加大。

材料二:某省省委领导集体针对本省农业生产面临的困境,号召党员干部通过街区走访、召开民主座谈会、网络民意调查等途径,集思广益,问计于民,逐步形成了“以人为本、创新转型、绿色生态、高效多元”的现代农业发展思路,提交省人大讨论并表决通过,为全省的农业发展指明了方向。

同类题2

阅读理解

                                                                                 Is There Life on Earth

    There was great excitement on the planet of Venus this week. For the first time Venusian scientists managed to land a satellite on the planet Earth, and it has been sending back signals as well as photographs ever since.

    The satellite was directed into an area known as Manhattan(named after the great Venusian astronomer Prof. Manhattan, who first discovered it with his telescope 20,000 light years ago). Because of excellent weather conditions and extremely strong signals, Venusian scientists were able to get valuable information as to the feasibility(可行性)of a manned flying saucer(飞碟)landing on Earth. A press conference was held at the Venus Institute of Technology.

    “We have come to the conclusion, based on last week's satellite landing,” Pro. Zog said, “that there is no life on the Earth.”

    “How do you know this?” the science reporter of the Venus Evening Star asked.

    “For on thing, Earth's surface in the area of Manhattan is composed of solid concrete and nothing can grow there. For another, the atmosphere is filled with carbon monoxide and other deadly gases and nobody could possibly breathe this air and survive.”

    “What does this mean as far as our flying saucer program is concerned?”

    “We shall have to take our own oxygen with us, which means heavier flying saucer than we originally planned.”

    “Are there any other risks that you discovered in your studies?”

    “Take a look at his photo. You see this dark black cloud floating over the surface of Earth?” We call this the Consolidated Edison Belt. We don't know what it is made of, but it could give us a lot of trouble and we shall have to make further tests before we send a Venus Being there.”

    “If what you say is true, won't this set back the flying saucer program several years?”

    “Yes, but we shall proceed as soon as the Grubstart gives us the added funds.”

    “Pro. Zog, why are we spending billions and billions of zilches to land a flying saucer on Earth when there is no life there?

    “Because if we Venusians can learn to breathe in an Earth atmosphere, then. We can live anywhere.”