测量开口容器液位时，压力计指示压力P与液位H被测介质的重度r之间的关系式是什么？

真分数和假分数比，真分数（　　）假分数．

A．大于

B．大于或等于

C．小于

D．小于或等于

阅读下面短文，根据小题的具体要求，简要回答问题。

Their round bodies, round flat noses and large ears often remind us of bears every time we see koalas. Probably that’s why these animals are often referred to as koala bears. Koalas are natives of Australia. However, they aren’t found all over the continent. The habitat of koala bears  is eastern regions of Australia and South Australia.

Koalas are found where there are enough forests of eucalyptus(桉树) trees. The association of koalas and eucalyptus trees is due to the fact that these animals feed on the leaves of eucalyptus trees. But that’s not all. In addition, the trees also serve as the homes of the koalas.

Koalas grow around 27 to 36 inches tall and weigh 5 to 9 kilograms on average. Male kaolas are larger than the females. Life can stretch up to 17 years.

Like many other animals, the habitat of koala bears is fast decreasing due to deforestation and quick urbanization(都市化). However, efforts by some scientists and animal lovers have successfully introduced these creatures back in certain parts of Australia.

小题1:What do Koalas look like ?      (回答词数不超过3个)

小题2:Where is the main habitat of koala bears in the world?     (回答词数不超过8个)

小题3:What do eucalyptus trees provide koalas with ?        (回答词数不超过3个)

人民论坛《千人问卷》调查组对“鸟巢一代”这一群体的“人生价值观”进行了广泛调查。调查显示：

（注：“鸟巢一代”即“80后”、“90后”这些新生代）

（1）从这份调查中， 居于首位。请利用课本知识分析，为什么人要有理想？

（2）青少年要实现理想，应该做些什么？

（3）假如你参与调查的话，你的选择是什么？要实现你的选择，我们应该怎么做？ 

什么叫离心泵的轴向推力，轴向推力是如何产生的？

尺度基准可用测距仪测定。