It can be either a or b.. I suggest go with b
Electro magnetism theory cover the basic principle of electro magnetism : experimental basis.
Electromagnetism is defined as an attraction between two partical.
Didn’t you just make a question right now?
It was quite difficult to understand what you need. Anyway, I've got it. I guess you need to much all the terms to each sentence. So I think I've done it right. Check it out:
1.an electronic index of books - <span>B. computer catalog
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2.a device which categorizes and locates web sites - </span><span>H. search engine
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3.to draw a conclusion - </span>D. infer<span>
4.a block of information stored in an HTML file on a server - </span><span>A. web page
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5.the table of contents of a web site - </span><span>G. home page
</span><span>
6.a software package which retrieves information from any or all available Internet servers - </span><span>I. browser
</span><span>
7.a highlighted word or phrase within a web page which acts as a "bridge" to another web page or site - </span><span>F. hyperlink
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8.a topic sentence - </span><span>C. key sentence
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9.a term which aids in narrowing a web search - </span>E. keyword
