摘要:1.数词+单数名词.如:20-minute 20分钟的 It's 20-minute walk.步行20分钟的路程. second-class 二等的 That's the second-class room. 那是个二等房间. 500-word 五百字的 This is a 500-word composition. 这是一篇五百字的文章.

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在物理学中,磁场的强弱用磁感应强度(用字母B表示,国际单位是特斯拉,符号是T)来表示,磁感线越密的地方,磁场越强,磁感应强度B越大.

(1)在图20中,甲为某磁极附近磁感线的方向和分布的示意图,由图可知,该磁极为 ▲ 极,若在l处放置一个小磁针,当小磁针静止时,其指向应是图乙中的  ▲   .
(2)磁敏电阻阻值的大小随磁场的强弱变化而变,图丁是某磁敏电阻R的阻值随磁感应强度B变化的图象,据图线可知,磁敏电阻的阻值随磁感应强度B的增大而▲ .图线没有过坐标原点,说明  ▲  .
(3)王强设计了一个可以测量该磁敏电阻R的电路如图丙所示,(其中磁敏电阻所处的磁场未画出).将该磁敏电阻R放置在磁场中的位置某处,测出电阻后,利用R—B特性曲线可以读出相应的磁感应强度.
①在图甲磁场中1处,测得的数据如图20表中所示,则该磁敏电阻的测量值为 ▲ Ω. 
②根据该磁敏电阻的R-B特性曲线可知,1处的磁感应强度为   ▲    T.
③在实验过程中,仅将磁敏电阻从1处移至2处,其它条件不变,那么电流表的示数
▲   (填“增大”、“减小”或“不变”).
④依据上述方法获得的磁感应强度B的测量值与该点实际值存在不小的误差,为尽可能准确反映空间某点磁场的强弱,你认为在选择磁敏电阻时应注意什么问题?
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Reading comprehension.
                                                        
        Do you feel a little sleepy after lunch? Well, that's normal. Your body naturally slows down then.
What should you do about it? Don't reach for a coffee! Instead, take a nap. 
        There are many benefits of a daily nap. First of all, you are more efficient after napping. You
remember things better and make fewer mistakes. Also, you can learn things more easily after taking
a nap. A 20-minute
nap can reduce information overload. It can also reduce stress, Finally, a nap may increase your self-
confidence and make you more alert. It may even cheer you up.
         But, there are some simple rules you should follow about taking a nap. First, take a nap in middle
of the day, about eight hours after you wake up, Otherwise, you may disturb your sleep-wake pattern.
Next, a 20~30 minute nap is best. If you sleep longer, you may fall into a deep sleep. After waking from
a deep sleep, you will feel worse. Also, you should set an alarm clock. That way, you can fully relax
during your nap. You won't have to keep looking at the clock and you won't oversleep.
        Now, the next time you feel sleepy after lunch, don't get stressed. Put your head down, close your
eyes, and catch forty winks.
        Choose the best answer from A. B. C or D according to the passage.
1.What is the main idea of this reading?
[     ]
A.Why children take naps.
B.How to sleep deeply.
C.Why napping is good.
D.The problems with napping.
2.According to the reading, what is not a benefit of napping?
[     ]
A.It improves you memory
B.It makes you feel happier.
C.It gives you more self-confidence.
D.It makes you stronger.
3.What is a good rule for taking a nap?
[     ]
A.Use an alarm clock.
B.Nap eight hours after waking up.
C.Sleep for about half an hour.
D.All of the above.
4.What is the best napping schedule?
[     ]
A.Two 60 minute naps per day.
B.One nap each day.
C.Napping only in the evening.
D.Napping only in the morning.
5.Which may occur if an alarm clock is not used?
[     ]
A.You may relax more.
B.You may feel too nervous to relax.
C.You may forget an important meeting
D.You may not reduce your napping time.
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