经济基础是( )。A．一切社会关系的总和 B．一切经济关系的总和 C．所有生产关系的

下列关于生理性带下的描述，错误的是 （）

A.色白或无色透明

B.质地粘稠

C.其量适中

D.无特殊气味

E.从 * * 内排出的一种阴液

维生素A的特点不包括（）

A.对酸和碱稳定

B.脂肪酸败可引起严重破坏

C.摄入过多可引起中毒

D.是黄素酶的辅酶成分

E.抗氧化作用

The volcano is one of the most surprising frightening things of nature. Maybe you have seen pic­tures of these " fireworks " of nature. Sometimes when a volcano erupts, a very large wall of melted rock moves down the side of a mountain. It looks like a " river of fire". Sometimes volcanoes ex­plode, throwing the melted rock and ashes high into the air. But where does this melted rock come from?

The earth is made up of many layers (层). The top layer that we see is called the crust. Under the crust are many layers of hard rock. But far, far beneath the crust the rock is so hot that it is soft. In some places it even melts. The melted rock is called magma. Sometimes the magma breaks out to the surface through cracks (裂缝) in the crust. These cracks are volcanoes.

Most people think of mountains when they think of volcanoes. But not every mountain is a volca­no. A volcano is simply the opening in the earth from which the magma escapes. The hot magma, or lava as it is called, cools and builds up on the surface of the earth. Over thousands of years, this pile of cooled lava can grow to be very, very big. For example, the highest mountain in Africa, Kilimanja­ro, is a volcano. It rises more than 16,000 feet above the ground around it.

8. The underlined word "erupts" means ______.

A. moves down   B. breaks away    C. builds up       D. suddenly throws out lava

9. Which words in the passage have the same meaning as "melted rock"?

A. volcano and crust                B. crust and hard rock

C. magma and lava                D. volcano and magma

10. Which is the correct order of the layers of the earth (beginning with the top layer)?

A. crust — hard rock — magma — soft rock

B. crust — hard rock — soft rock — magma

C. agma — soft rock — hard rock — crust

D. volcano — cracks — magma — crust

11. The best title of the passage should be______.

A. The Volcano        B. Kilimanjaro Volcano   C. The Mountains   D. The Melted Rock

公文写作的步骤是什么？

金银充当货币后，可以与一切商品交换。这说明()

A．金银作为货币代表着一种社会生产关系
B．金银可以避免通货膨胀
C．金银与物品的交换更加方便了
D．金银具有充当货币的天然属性