第一节 （共 15小题；每小题2分，满分 30分）
阅读下列短文，从每题所给的 A、B、C和 D 四个选项中选出最佳选项。
A
An egg sinks to the bottom if you drop it into a glass of ordinary drinking water but what happens if you add salt? The results are very interesting and can teach you some fun facts about density(密度)．
What you'll need：
* One egg * Water * Salt * A tall drinking glass
Instructions：
Pour water into the glass until it is about half full.
Mix in lots of salt(about 6 tablespoons)．
Carefully pour in plain water until the glass is nearly full (be careful not to mix the salt water with the plain water)．
Gently lower the egg into the water and watch what happens.
What's happening?
Salt water is denser than ordinary tap water. The denser the liquid is, the easier it is for an object to float in it. When you lower the egg into the liquid it drops through the normal tap water until it reaches the salt water, and at this point the water is dense enough for the egg to float. If you were careful when you added the tap water to the salt water, they would not mix, enabling the egg to amazingly float in the middle of the glass.
21. Which of the following is the CORRECT order？________
①Mix in lots of salt.
②Gently lower the egg into the water.
③Carefully pour in plain water until the glass is nearly full
④Pour water into the glass until it is about half full.
A. ④②①③ B. ④①③②
C. ①④③② D. ③④①②
22. Why can the egg float in the water according to the passage？________
A. Because ordinary tap water is denser than salt water.
B. Because ordinary tap water is as dense as salt water.
C. Because the denser the liquid is, the easier it is for an object to float in it.
D. Because the more the liquid there is, the easier it is for an object to float in it.
23. What will happen if you drop an egg into a glass of water with about 6 tablespoons of salt？ ________
A. It will float in the water.
B. It will sink to the bottom.
C. Nothing will happen.
D. The result is not known.
【答案】21. B 22. C 23. A
【解析】
【分析】本文是一篇说明文，是一个关于密度的鸡蛋实验。
【21题详解】
细节理解题。根据Instructions部分的“Pour water into the glass until it is about half full.Mix in lots of salt(about 6 tablespoons)．Carefully pour in plain water until the glass is nearly full (be careful not to mix the salt water with the plain water)．Gently lower the egg into the water and watch what happens.（将水倒进玻璃杯直到半满。加入大量的盐(大约6汤匙)。小心地倒入白水，直到杯子几乎满了(注意不要把盐水和白水混合)。轻轻地把鸡蛋放入水中，看看会发生什么。）”可知，正确的排序是④①③②，故选B。
【22题详解】
推理判断题。根据What's happening?部分的“Salt water is denser than ordinary tap water. The denser the liquid is, the easier it is for an object to float in it.（盐水比普通自来水的密度大。液体密度越大，物体就越容易漂浮在其中。）”可知，鸡蛋之所以能浮在水里是因为液体的密度越大，物体就越容易漂浮在其中。故选C。
【23题详解】
细节理解题。根据Instructions部分的“Mix in lots of salt(about 6 tablespoons)（加入大量的盐(大约6汤匙)）”和最后一段的“When you lower the egg into the liquid it drops through the normal tap water until it reaches the salt water, and at this point the water is dense enough for the egg to float.（当你把鸡蛋放入液体中时，它会在普通的自来水中下降，直到它到达盐水，此时水的密度足够让鸡蛋漂浮起来。）”可知，如果你把一个鸡蛋扔进一杯加了6汤匙盐的水中，它就会浮在水中，故选A。
