A. B. C. D. E.  

在《物质的构成》一课中，老师做过这样的演示实验：先在量筒中倒入黄豆，再倒入芝麻，记下总体积；再将量筒反复颠倒摇晃，记下混合后的总体积．下列有关这个实验的说法正确的是（　　）

如图所示，质量为m的小球从距离地面高H的A点由静止开始释放，落到地面上后又陷入泥潭中，由于受到阻力作用到达距地面深度为h的B点速度减为零．不计空气阻力，重力加速度为g．关于小球下落的整个过程，下列说法中正确的有（   ）

已知等差数列{a_n}前四项中第二项为606，前四项和S_n为3834，则该数列第4项为（　　）

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

    Last Saturday afternoon, a charity sale held on our school playground. Although it was no easy task, students active participated in it.

    To organize it successfully, we' made full preparations. After the sale, from the students we collected variously second-hand goods which were still in good condition and classify them. Then came the big day. With all the teachers and students involve, the activity turned out to be successful. We raised 5,000 yuan for total at the end of the activity. All the money we raised up will go to the students from poor family to help finish their studies. It's so a meaningful activity that students look forward to the next charity sale.