The third advantage of electronic copies is that they occupy millimeters of space on a magnetic disk rather than meters on a shelf. Expanding library buildings is increasingly costly. The University of California at Berkeley recently spent $46 million on an underground addition to house 1.5 million books—an average cost of $30 per volume. The price of disk storage, in contrast, has fallen to about $2 per 300­page publication and continues to drop.

　　20．The best title for this passage would be “________”．

　　A．Three Benefits of Libraries

　　B．Libraries Going Digital

　　C．Space­saving E­learning

　　D．Security of Electronic Reading

　　21．Which paragraph(s) in the text offer(s) further explanation of the central idea?

　　A．Paragraphs 2, 3 and 4

　　B．Paragraphs 3 and 4

　　C．Paragraphs 2 and 4

　　D．Paragraph 4

　　22．Which one of the following is mentioned as an advantage of e­libraries?

　　A．Old manuscripts can be moved more easily.

　　B．Materials can be examined without being touched.

　　C．Fewer staff will be required in libraries.

　　D．Libraries will be able to move underground.

　　23．What does the word “scrutinize” probably mean?

　　A．Keep for a while.

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