题目内容

一、单项选择题（本大题共10小题，每小题2分，共20分）
在每小题列出的四个备选项中只有一个是符合题目要求的，请将其代码填写在题后的括号内。错选、多选或未选均无分。
1．设A，B，C为同阶方阵，下面矩阵的运算中不成立的是（）

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下面各图都是正方体的表面展开图，若将它们折成正方体，则其中有两个正方体各面图案完全一样，它们是()。

A. (3)和(4) B．(1)和(3) C．(2)和(3) D．(2)和(4)

Crystal Ear One day a friend asked my.wife Jill if I wanted a hearing aid.“He certainly does.”replied Jill.After hearing about a remarkable new product.Jill finally got up the nerve to ask me if I'd ever thought about getting a hearing aid.“No way,”I said.“It would make me look 20 years older.”“No，no.”she replied.”This is entirely different.It’s Crystal Ear!”
Jill was right.Crystal Ear is different—not the old. Styled body worn over-the earaid，but all advanced personal sound system so small that it’s like contacts(隐形眼镜)for your ears.And Crystal Ear is super-sensitive and powerful.too.You will hear sounds your ears have been missing for years.Crystal Ear will make speech 10uder,and the sound is pure add natural.
I couldn’t believe how tiny it is.It is smaller than the tip of my little finger and it’s almost invisible When worn.There are no wires。no behind—the.ear device.Put it in your ear and its ready—to-wear mold(形状)fits comfortably.Since it’s not too loud or too tight，you may even forget that you’re wearing it! Use it at work or at play.And if your hearing problem is worse in certain situations，use Crystal Ear only when you need it.
Hearing loss，which Occurs typically prior to teenage years，progresses throughout one’s lifetime.A1though hearing loss is now the world’s number one health problem，nearly 90 percent of people suffering hearing 10SS choose to leave the problem untreated.For many millions，treating hearing 10SS in a conventional way can involve numerous office visits，expensive testing and adjustments to fit your ear.Thanks to Crystal Ear，the“sound solution”is now convenient.
Almost 90 percent of people with mild hearing loss，and millions more with just a little hearing drop-off(下降)，can be dramatically helped with Crystal Ear.More over, its superior design is energy-efficient，so batteries can last months.Crystal Ear is now available to help these people treat their hearing loss with a small hearing amplifier(放大器).
第6题：Initially the writer did not want t0 buy a hearing aid because

A. it would make him look old．
B. it would make him nervous．
C. it was too expensive．
D. it was old-styled．

Smith’s idea has extensive applications.

A. Right
B. Wrong
C. Not mentioned

如下图所示，一根轻弹簧下端固定，竖立在水平面上。其正上方A位置有一只小球。小球从静止开始下落，在B位置接触弹簧的上端．在C位置小球所受弹力大小等于重力，在D位置小球速度减小到零。
下列对于小球下降阶段的说法中，正确的是______。

A. 在B位置小球动能最大
B. 在C位置小球动能最小
C. 从A→D位置小球重力势能的减少小于弹簧弹性势能的增加
D. 从A→C位置小球重力势能的减少大于小球动能的增加