A、A real book. B、A computer file. C、A handheld device. D、A piece of paper. B短文开头即对电子书下定义，指出它是以电脑文档的形式出现的，故B为答案。

E-books are bringing about a profound revolution in the way books are read. In the future it’s likely we’ll get used to clicking instead of flipping to read the next page. [13]An e-book, short for "electronic book." is any published work-containing text and/or graphics-stored as a computer file. Users can read them by downloading the files onto a desktop computer, laptop or portable device such as a personal digital assistant (PDA). They can also use a handheld gadget designed specifically for reading digital books. Downloading books onto a desktop or handheld device is becoming more and more common. Books can be downloaded from the Internet at a much lower price than it would cost to buy paperbacks. Some websites even offer downloading free-of-charge as many writers and websites are happy just to gain some exposure. [14]But experts believe these services won’t remain free for long, as it is not the way to make profits.
    Handheld e-book devices certainly have a long way to go before gaining widespread acceptance. Some book lovers say they are used to paperbacks and that the cold, clumsy machines are uncomfortable to the touch, not to mention the loss of the pleasure of holding a book in the soft, yellow glow of a bedside light. [15]E-book developers and producers are aiming at improving the technology to make e-books more like real books to attract more readers. They have been making great strides.
13. What is an e-book like?
14. Why did experts believe downloading free-of-charge would not last long?
15. How well have e-book developers and producers been doing to attract more readers?