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问题 选择题

下列说法中正确的是[ ]

A．物质的量就是物质的质量

B．阿伏加德罗常数就是6. 02×1022

C．6. 02×1023mol-1叫做阿伏加德罗常数

D．科学上规定含有阿伏加德罗常数个粒子的任何粒子集合体为1 mol

答案

答案：D

问答题

                                                                            人类的眼睛

       人类的眼睛很像一架照相机，眼睛与照相机的不同之处是：人的眼睛是通过调节晶状体的弯曲程度，改变晶状体的焦距来获得清晰的、              、缩小的实像，如图所示；普通照相机是在物距确定的情况下通过改变像距使像变得清晰，由眼睛的调节作用所能看清楚的最远点，叫远点，正常眼的远点在极远处；眼睛所能看清楚的最近点，叫近点，正常眼的近点约距眼睛10㎝。眼睛是人体的重要器官，长时间的用眼，如看书、看电视、计算机，都可以引起眼睛的疲劳，眼睛疲劳的常见症状是头疼脑胀、眼睛发干。看物体时间较长也不易感到疲劳的距离叫明视距离，正常眼的明视距离为25㎝。

（1）请把文中像的性质补充完整。

（2）人的眼睛是通过改变晶状体的             来获得清晰的像；普通照相机是在物距确定的情况下通过改变              使像变得清晰。

（3）根据上文，你认为人的正常眼的观察范围是：[ ]

A．0~10㎝　

B．10~25㎝

C．从10㎝到极远处

D．0~25㎝

（4）如何预防眼睛疲劳，请你提出一条合理化建议：                                                                   。

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单项选择题

Imagine fishermen walking down to the seashore, ready to carry out their early morning routine of preparing their boats and net. (51) they hope for a good catch of fish. But to their (52) , a horrible sight meets their still sleepy eyes. Thousands of fish have been washed ashore dead. The cause of this mass destruction—A red tide!

Red tides are a global (53) . They have been observed on both the Atlantic and the Pacific coasts of the United States and Canada. They have also occurred in many other places. Though relatively few people are (54) them, red tides are not new.

In the Philippines, a red tide was first seen in the province of Bataan in 1908. Since then, red tides have been seen in many other (55) . A Philippines red tide expert told us that " (56) the fish kills, the Philippines has documented 1, 926 eases of dead shellfish poisoning caused by red tides. "

The term "red tide" (57) the discoloration of water that sometimes occurs in certain areas of the ocean or sea. Although the color is often red, it may also be (58) of brown or yellow. The World Book Encyclopedia reports that "the discolored areas may range from (59) a few square yards to more than 2,600 square kilometers. "

What causes such discoloration Red tides are generally caused by several species of single-celled organisms. These tiny organisms have hair-like projections which they use to (60) themselves in water.

57().

A. applies to

B. sums up

C. copes with

D. leads to
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