Every object has weight. But the center of its weight is not always in the middle of the object. If the top of an object is heavier than its bottom, it will fall over easily. We say that its center of gravity is high. But if the bottom is heavier, it won't fall easily. Then we say that its center of gravity is low.
    Look at the first picture. This empty box must fall over, because its center of gravity (C) is not above the line of its bottom (AB).
Now look at the second picture. There is some heavy iron in the bottom of this box. It will not fall, because its center of gravity is above its bottom.

下列对孔子及其思想的说法不正确的是（   ）

下列标点符号的用法判断不正确的是（    ）

原子结构模型的演变图如图，其中①为道尔顿实心球式原子模型，②为卢瑟福行星运转式原子模型，③为汤姆生葡萄干面包式原子模型，④为近代量子力学原子模型，⑤为玻尔轨道式原子模型．

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这些模型的历史演变顺序是（　　）

漫画《禁》中学校的做法(    )

①有利于推动学校同步发展           ②有利于维护社会的公平正义

③有利于维护社会稳定与发展        ④不利于孩子成长,是非正义的行为