题干

草履虫的呼吸主要是通过(  )完成的.

A:纤毛

B:表膜

C:口沟

D:伸缩泡

上一题 下一题 0.0难度 选择题 更新时间:2016-12-12 03:04:17

答案(点此获取答案解析)

B

同类题1

根据短文理解,选择正确答案。

    I was feeling really down because my long-time friend had died. Then I started a six-week volunteering at a nursing home all day even Saturday. My duty was to serve the meal and clean up. One day I was told to go to Room 117 to make sure the patient was all right. I found a boy of eight sitting in bis bed watching a movie. I was shocked to see a child in this seemingly forgotten nursing home for the old. He was so small and weak that you had to look closely to find him. I grabbed his medical chart and found out :he had a terminal(绝症的) illness.

    We started to talk, and I found out that his family rarely visited, and all he did every day was watching TV I wanted to cry for him, and for my lost friend. As we talked, he had a smile on his face, and I asked him why and how he still managed to stay happy.

    He thought for a moment, and then said that too many people were dead even before they died. They walked around feeling that God had cursed(诅咒) them and they had nothing to live for.

    The boy said that he would not be like that. He woke 'every morning thankful to see another sunrise. He kept his window open so that he could smell the flowers and feel the heat of the sun. He also said that he had hope.

    "Too many people haven't seen much of that around here." He said, "Life is full of hope and we need to live life before it is gone."

    I don't know what happened to him. I guess he passed away, but his lesson lives on. I now wake up and live each day to the fullest. The key to life is not money or fame, but the lesson we learned from it.

同类题5

阅读下面文章,完成后面小题。

魏景超:用心守护植物健康成长

    魏景超(1908~1976),我国著名植物病理学家、农业教育家。1930年毕业于金陵大学园艺系。1933年,他参加清华大学公费留美研究生考试,名列全国第一。1937年获美国威斯康星大学博士学位,后回国任职,在水稻病害研究、真茵分类学及植物病毒学研究上作出了卓越的贡献。

    魏景超幼年目睹农民颠沛、饥寒交迫,深感只有振兴农业,才能解决民生问题。立志于兴农的他,大学毕业后就以优异的学习成绩获“金钥匙”奖,并成为“斐陶斐”学会会员。在美国留学期间,他利用可利用的时间和设备,放弃节假日休息,参加暑期学校学习、参观实验室和农场、访问老教授,以获取知识,汲取经验和新的见解。在学校里,他更是抓住学校资源,勤奋刻苦。图书馆里,他埋头钻研;实验室里,他观察切片、制作标本,孜孜不倦。爱思、善学、勤问的他努力摄取国外新知识、新技术,汇集大量的宝贵文献与读书笔记。可惜的是,回国正值抗日战争期间,魏景超积累了四年的书籍、笔记随交运的美国轮船一起在日机轰炸下沉于太平洋底。

    回国后执教于金陵大学的魏景超,面对国内农业教材与国际水平的差距,边执教边精心编写讲义、教材。外出采集标本、调查农作物病虫害情况、拍摄照片、绘制讲解图表等,身体力行。他先后讲授过普通和高级植物病理学、作物病害、真菌学、细菌学、植物免疫学和病毒学等课程。出版有《普通植物病理学》《植物病理学实验指导》《真菌重要目、科、属分类检索表》等优秀教材、书籍。

    魏景超十分注重课前准备工作,细致地整理授课内容、思路,并结合当时最新研究成果的讲解以扩充学生的知识面,确保课堂的高效授课。课堂上,他条理清晰、深入浅出;实验室里,他仔细观察每个学生的操作,及时指正规范;野外实习时,他认真传授观察作物病情和采集标本的知识。对学生循循善诱的他更注重因材施教,对低年级学生侧重基础知识的把握,对高年级学生侧重独立探索、学习的能力培养。对跟随他研究学习的十几个学生,他按各人的进修计划进行个别指导,耐心细致,诲人不倦。抗日战争期间,他常到外校兼课,将其所得资助家在沦陷区或家境困难的同学,竭力培养农业人才。他要求年轻助教作充分的课前准备,上课时还经常跟班听讲,对缺点加以指正,给予必要的示范。严谨的态度、躬亲的姿态,用“心”教学的魏景超对学生和其他老师产生了深远的影响。

    在水稻病害方面,魏景超先后发表8篇重要的学术报告及论文。他实地调查试验,足迹遍布江、浙、沪、闽、粤、桂、皖等近10个省市地区。他编写了《水稻病原手册》,详细记载了我国已发现和国外报道过寄生于水稻的约250种微生物,对重要病原菌简要说明其诱致的症状、发病因素和防治方法。该书作为诊断稻病的工具书,多年来为国内外同行所采用或引用。

    在真菌分类学上,魏景超亦有卓越贡献。1948年,魏景超重新鉴定了番茄漆腐病的病原菌,更正了其所属类别,还澄清并鉴定了豇豆和大豆叶斑病病原菌。晚年的他辗转在病榻与书桌之间,日夜辛劳长达6年,完成了《真菌鉴定手册》,填补了我国真菌鉴定工具书的空白。

    在植物病毒学研究方面,魏景超历来重视科学研究解决生产实际问题。早在上世纪40年代初期。他在成都附近调查烟草和番茄病害。之后又致力于华东地区十字花科蔬菜花叶病的考察、研究,阐明了常见病害的症状、病原、寄主范围及防治方法。尤其在油菜病毒研究方面,总结出油菜远村育秧、避蚜防病毒的有效措施。

    晚年身患重病的魏景超,仍心系国家。1956年江苏省昆山县油菜田发生严重病害之际,他在同志们搀扶下仍然在田间跋涉,观察油莱病情,同行者无不感动。

“以振兴中国农业为己任”,上下求索,魏景超用躬行的一生诠释了践行者的姿态。

(摘编自李姝昱《魏景超:用心守护植物健康成长》)

【相关链接】①分类研究并非易事,寻找理想标本,往往需要连续追索数年。有时能获得满意的结果,有时也会发生错误甚至失败,但魏景超坚持实事求是的精神,有错必纠,从不灰心丧气,总是再接再厉地干下去。(摘编自“魏景超纪念馆”)②一想到祖国多灾多难,倍受帝国主义的欺凌,他便忿然而起。他想自己是中国人,又是公费留学生,一定要刻苦学习,为国家争光,为民族争气。(摘编自《科普中国•科技名家风采录》)