注释：

1.       MP3 ：Internet上最流行的音乐格式，最早起源于1987年德国一家公司的EU147数字传输计划，它利用MPEGAudioLayer3的技术，将声音文件用1∶12左右的压缩率压缩，变成容量较小的音乐文件，使传输和储存更为便捷，更利于互联网用户在网上试听或下载到个人计算机。

2.       Philadelphia：费城[美国宾夕法尼亚州东南部港市]

3.       Woods Hole：美国马萨诸塞州的一个渔村，也是许多重要研究机构所在地，如： the Marine Biological Laboratory, the Sea Education Association 以及 the Woods Hole Oceanographic Institution,

4.       Mass.：Massachusetts 的缩写：马萨诸塞州，美国东北部的一个州。

5.       global positioning system (GPS)： 全球定位系统

6.       Science：美国的 Science 杂志为国际上著名的自然科学综合类学术期刊，在世界学术界享有盛誉。 Science 杂志创刊于1880年，该杂志具有新闻杂志和学术期刊的双重特点，每周除向世界各地发布有关科学技术和科技政策的重要新闻外，还发表全球科技研究最显著突破的研究论文和报告。

练习：

1.  Backpacks are convenient because

A) they can be very large

B) they can hold as many things as you want to carry.

C) your hands are freed to do other things.

D) you do not have to carry things with you.

2.  What is the most important feature of the backpack invented by Lawrence C. Rome and his colleagues?

A) It produces electricity for electronic devices while the wearer walks.

B) It can be used as  cell phones, GPS in the military actions or field studies. 

C) It is small and convenient.

D) It is light and easy to carry.

3.  The word “springs” in Paragraph 3 means

A) a small stream of water flowing naturally from the earth.

B) the season of the year, occurring between winter and summer.

C) the act or an instance of jumping or leaping.

D) a length of metal wound around, which returns to its original shape after being pushed.

4.  According to Paragraph 4, what does Rome plan to do?

A) To make the backpack more comfortable for the wearer.

B) To put the backpack on the market.

C) To test the advantage of the backpack.

D) To promote the backpack in a newspaper or on television.

5.  What is implied in “if you do get one eventually, just make sure to look both ways before crossing the street!”

A) You will be too excited to watch the traffic.

B) Enjoying electronic devices while walking may invite traffic accidents.

C) It is not possible for you to get such a backpack.

D) It is wise of you to have such a backpack.

答案与题解：

1.  C   第一段告诉我们，因为背包可以装许多东西，所以可以将双手解放出来做其它事情：to free your hands to do other things.

2.  A   第二段的第一句说，Lawrence C. Rome 及其同事们发明的这种背包，当背着背包走路时，会有电能产生；该段最后一句告诉我们，背包的这种性能可减少背包的重量，因为不必携带备用电池。

3． D   “springs”在此是弹簧的意思。spring是一个多义词：泉水（A）、春天（B）、弹跳（C）。

4． B   第四段最后一句的意思是：Rome计划将这种背包商业化，即，推向市场。A、C、D在文中均未提到。D的意思是为背包做广告。

5． B   这个句子的字面意思是：如果你终于得到这样的背包，过马路时一定要两面都看看。也就是说，不要因为同时玩着游戏、听着音乐、看着电视，太专注以致不注意来往车辆了。