题干

对下列图示的生物学实验的叙述中正确的有(     )

A:若图①表示制作装片,用显微镜观察正在发生质壁分离的紫色洋葱表皮细胞,可见其液泡体积逐渐变大,颜色逐渐变浅

B:若图②是用低倍显微镜观察洋葱根尖某视野中的图像,则要看清处于分裂期的细胞,应将装片适当向右移动

C:若图③表示将显微镜镜头由甲转换成乙,则视野中观察到的细胞的数目增多

D:若图④是利用2m×2m的样方调查双子叶草本植物苦荬菜的种群密度(圆圈表示个体),则该样方内苦荬菜的种群密度为2.5株/m2

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答案(点此获取答案解析)

D

同类题1

阅读理解

    Amy Maplethorpe, a first-year speech-language teacher at Raymond Ellis Primary School, used tennis balls, a hot glue gun, Mod Podge and a bit of paint to create two chairs that help students with sensory (感官的) problems.

    According to the school's Facebook page, which became very popular, the chairs provide a “different texture (质地) to improve sensory regulation (调控).”

    Maplethorpe told ABC News that the chairs will service about 15 to 20 students. Children with sensory problems often have a hard time “dealing with sensory information”. Things, such as coats, blankets and Maplethorpe's chairs, often comfort a student.

    Maplethorpe was excited to create the chair after seeing something similar on a website, and she made some changes to the idea.

    “I wanted to continue to help students with sensory problems at Ellis and provide a different kind of seat for the students,” she continued. “I was excited that this chair could help my students.''

    The two chairs are now in the school's sensory room, which was created recently, according to headmaster, Beth Kiewicz.

    “When a child's sensory needs are met, we then can move on to their needs in study,” Kiewicz, who has led the school for six years, told ABC News.

    Maplethorpe said the chairs have already made a difference for some of her students.

    “Students have become more patient, and have followed directions, while waiting for activities,” she said.

同类题3

某探究学习小组的同学欲验证“动能定理”,他们在实验室组装了一套如图所示的装置,另外他们还找到了打点计时器所用的学生电源一台,导线、复写纸、纸带、小木块、细沙若干.当滑块连接上纸带,用细线通过滑轮挂上空的小沙桶时,释放小桶,滑块处于静止状态.

1你是小组中的一位成员,要完成该项实验,则:①还需要补充的实验器材是____

2②某同学的实验步骤如下:用天平称量滑块的质量M.往沙桶中装入适量的细沙,让沙桶带动滑块加速运动,用打点计时器记录其运动情况,用天平称出此时沙和沙桶的总质量m.在打点计时器打出的纸带上取两点,测出这两点的间距L,算出这两点的速度v1与v2.他用沙和沙桶的总重力表示滑块受到的合外力,为了减小这种做法带来的实验误差,你认为在图示情况下还应该采取的一项操作是:____; 应控制的实验条件是:____

③若挑选的一条点迹清晰的纸带如下,且已知滑块的质量为M,沙和沙桶的总质量为m,相邻两个点之间的时间间隔为T,从A点到B、C、D、E、F点的距离依次为S1、S2、S3、S4、S5(图中未标出S3、S4、S5),则由此可求得纸带上由B点到E点所对应的过程中,沙和沙桶的重力所做的功W=____

该滑块动能改变量的表达式为△EK=____.(结果用题中已知物理量的字母表示)