题干

为了增强抗旱能力,保证今年夏粮丰收,某村新建了一个蓄水池,这个蓄水池安装了两个进水管和一个出水管(两个进水管的进水速度相同)一个进水管和一个出水管的进出水速度如图1所示,某天0点到6点(至少打开一个水管),该蓄水池的蓄水量如图2所示,并给出以下三个论断:①0点到1点不进水,只出水;②1点到4点不进水,不出水;③4点到6点只进水,不出水.则一定正确的论断是____ .

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同类题2

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    What do you think of robots? Will they work for humans in the future?  Maybe we can't answer it.But robots have 1 an important part in our daily life for several years .But in some science fiction movies, the robots are just like humans. Now they help humans with the housework and do the most 2 jobs.

    Many scientists believe that there will be such robots in the future.3they agree it may 4 hundreds of years. Scientists are now trying to make robots look like people and do the same things as us.

    But robot scientist James White 5 He thinks that it will be 6 for a robot to do the same things as a person7 it's easy for a child to wake up and know where they are. Mr. White thinks that robots won't be able to do this. But other scientists disagree. They think that robots will be able to talk to people 8 25 to 50 years.

    Robot scientists are not just trying to make robots look like people. For example, there are already robots working in factories. They do many 9 over and over again. People would not like to do such jobs and would get bored. But robots will10 get bored.

    In the future, there will be more robots everywhere, and humans will have 11 work to do. New robots will have many different12. Some will look like humans, and13 might look like snakes. After an earthquake , a snake robot could help look for people under buildings. That may not seem possible now, but computers, space rockets and even electric toothbrushes 14 impossible a hundred years ago. With the 15of science technology. We never know what will happen in the future! Let's work much harder to make robots serve us better!

同类题5

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细菌也有益

    ①人们都喜欢用美妙的词句、动人的诗篇去赞美那些湖光山色、花香鸟语,却很少有人赞美过细菌。一提起细菌,人们总会预感到一种不祥之意,因为它能传染疾病,给人们带来痛苦。可是,谁又能想到细菌也有有益的一面呢?

    ②在日常生活中,我们每时每刻都在跟细菌打交道。细菌非常微小,只有在显微镜下才能看见。可是有些细菌对人类却起了重大作用。譬如,在工业上,可以利用细菌勘探石油;在日常生活中,像我们食用的醋泡菜和我们饮用的红茶菌,都是用细菌制成的;还有农作物生长也离不开细菌。大家知道农作物要想长好,土壤必须肥沃,而土壤的肥沃就是靠有些细菌来发挥作用的。

    ③关于土壤中细菌的作用,科学家曾经做过这样的观察:在1克重的土壤中有1亿到几十亿个生物,其中大部分是细菌。土壤细菌能把土壤中不能被植物直接吸收的养料分解成植物所需的物质。另外,土壤细菌还能制造各种抗生素和微生素,帮助植物抵抗病菌,促进植物生长。但是也有些细菌对植物有害,它们能吞食养料分解成异物,使土壤板结。

    ④因此,我们要消灭有害细菌,确保有益细菌的生长和繁殖,充分发挥它对人类的作用。不久的将来,一定会有更多的细菌被人们开发和利用。