题干

如图为某同学在显微镜下观察到的细胞图象,仔细观察并分析:从像A变成像B是做了怎样的处理?(  )

①低倍镜换成了高倍镜②向右下移动了玻片③向左上移动了玻片④把大光圈换成了小光圈.

A:①③

B:①④

C:②③

D:①②④

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A

同类题1

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食品添加剂中的“白富美”

    ①很多人觉得食品添加剂不是“好东西”,希望食品都能“零添加”;也有很多人觉得“天然成分”比“人工合成的化学物质”更安全,所以要选择“纯天然”。但人们或许不知道,有些食品添加剂并不会危害健康,甚至加了比不加更有益;也有些食品添加剂本来就是“天然成分”,可谓食品添加剂中的“白富美”。

    ②在这些有益健康的食品添加剂中,首先要说一说营养强化剂,它们是食品添加剂中的一大类,包括了人体所需要的多种维生素、矿物质(钙、铁、锌、硒等)和其他营养物质(深海鱼油、乳铁蛋白等)。

    ③对于某些特殊人群,营养强化剂是必需的,比如一些婴儿的母亲没有母乳,孩子需要吃婴幼儿配方乳粉,这些乳粉就必须加入多种营养强化剂,配合乳清蛋白等其他成分就可以最大程度满足婴儿的全部营养需求,使宝宝健康成长。

    ④近年来,粗粮受到越来越多的追捧,其中很重要的原因就是粗粮富含对人体有益的膳食纤维。食品添加剂中有一大类叫增稠剂,一般是胶类、多糖类、糖醇类和改良淀粉类物质,其中有很多品种都是来自于天然食材的膳食纤维。比如,提取自豆类植物的刺云豆胶、槐豆胶、瓜尔胶、葫芦巴胶、决明胶、皂荚糖胶、田菁胶、大豆多糖;由微生物发酵产生的黄原胶,可得然胶;提取自海藻的卡拉胶、海藻酸钠、海萝胶;提取自其他植物的黄蜀葵胶、亚麻籽胶、沙蒿胶、阿拉伯胶、果胶;提取自动物皮、骨和结缔组织的明胶;还有近些年保健品中较为常见的甲壳素、葡聚糖、壳聚糖也都是膳食纤维。

    ⑤另外,安全高效的抗氧化剂特丁基对苯二酚也是对健康有益的一种食品添加剂,因为抗氧化剂具有清除自由基的能力。当然,对于那些听到化学名词就心里不舒服的“自然爱好者”,另一些抗氧化剂可能更适合他们的胃口,比如维生素C和维生素E。还有一些抗氧化剂是直接从植物中提取的,比如茶多酚、甘草抗氧化物、迷迭香提取物、竹叶抗氧化物等,它们也包含多种抗氧化成分,不过在食品中添加的量也比较少。

    ⑥食品添加剂里面还有些品种听起来十分“高端”“洋气”,比如番茄红素、蜂蜡、石榴果汁浓缩物、薰衣草油、紫苏油等。甚至有些百姓厨房里的常见调料也算食品添加剂,比如八角、茴香、丁香、肉桂等。另外,目前中国人的饮食结构中90%是来自鲜活农产品,仅有10%左右来自加工食品,食品添加剂的威胁其实没有我们想象得那么可怕,而且适当吃一些具有营养强化作用的加工食品,是有益无害的。

(文段来源于2015年湖南邵阳市中考语文试题)

同类题5

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    For the past 15years, factory owner Kamal Parmar has been running an after-school program for slum kids in Ahmedabad, India, helping them with basic skills like reading and writing and even preparing for their school tests.

    Parmar's story began one afternoon 15 years ago. He stopped a few kids returning home from the local school and took their exam paper and asked them a few questions. Shockingly, he made a shocking discovery--the students, even the older ones, knew nothing about reading except the alphabet. And that left him thinking that something should be done for these children.

    So he invited the kids to visit his workshop every evening, where he set up a temporary classroom with metal desks. The shabby school started off with 10 students. Today, the Footpath School has a total of 155 students and many of the kids that Parmar has taught in the past 15yearshav e gone to attend college and build successful careers.

    Despite having studied only till the seventh grade, he has been able to teach the kids by inventing creative techniques. He asks them to read first and then to form questions on their own and read them out. In this way, many kids learn all seven subjects in six months.

    Parmar's family are very supportive of his project and are proud to see how much of an impact he has had on the kids. His students love him. Ten of his ex-students are currently serving as teachers at the school and he doesn't have to employ any teachers.

    For those who are inspired by his story, but can't actually volunteer at school, Parmar has a simple piece of ads ice: “Try to educate just one child a year, and see the difference it makes to the society.”