一个三角形和一个平行四边形的底相等，面积也相等．如果三角形的高是8分米，那么平行四边形的高是____分米

--那辆自行车是你的吗？--是的，它是我的。

-Is that bike ____?

-Yes, it's ____.

    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.