长方体、正方体、圆柱和圆锥的体积都可以用底面积乘高计算。（判断对错）

阅读短文，从方框中选择恰当的词语并用其适当形式填空，使短文完整、通顺。每个限用一次。

choose，think of, quiet，bring，like，idea， it，make，instead，plant

    Linda and Laura were very excited because it would be their mother's birthday next Monday. Their mother loved ____and she knew a lot about them. On Thursday, the two girls pretended (假装) that they were going out to buy eggs and bread with their father. ____they went to the plant store where their mother often went. With their father's help, they ____a plant with beautiful flowers. They were sure their mother would like ____.
    When they got home，their mother was busy in the kitchen, so they ____ carried the plant to their room. They wondered where they could put it because they wanted to give their mother a surprise on Monday. They looked around the room carefully. Finally, the two young girls had a(n) ____. They put the plant in a big box and ____it to the top of the bookcase. After it was done, they were very happy.
However, no one ____watering the plant over the next few days. They just treated (对待) the plant ____any other gift. When their mother's birthday came, they opened the box and found a dead(枯萎的) plant with dry flowers, but it still ____their mother happy.

设，，O为坐标原点，动点满足，，则的最大值是                      （   ）

“国家无非是一个阶级镇压另一个阶级的机器,这一点即便在民主共和制下也丝毫不比君主制差。”这句话表明 (   )

$\frac{7}{12}$ 的倒数是____，1的倒数是____。