In the last few years the popularity of eBooks has exploded．The advantages are clear：You can carry as many books with you as you want．You can simply download every book you like and instantly start reading instead of having to wait for the book to arrive by mail．
However，one thing hadn't changed．If you wanted to rent a book you were still forced to use hardcopy books．Until now that is． Amazon．com recently announced the start of a new program where you can rent eBooks．
Where to rent eBooks？
As mentioned before，Amazon．com is the first and currently the only retailer (零售商) that has a program in place for renting eBooks．Luckily，Amazon is the largest online retailer in the world and their eBook assortment (分类) is massive．They are also the producer of the Kindle，the most popular eReader，which means you can be sure that the eBooks you rent will work．
You can currently only rent eTextbooks．But this is likely to change as soon as word gets out that you can save money by renting eBooks．
Why rent eBooks at Amazon？
* Save money：Save up to 80% of the normal price of the eBook．
* Decide how long you rent：From 30 days to 360 days，you decide how long you want it．You can extend the time by as little as a day．Or simply buy the eBook if you want to keep it after all．
*Use any device：If you rent an eBook from Amazon，you can read it on your PC，Mac，iPad，iPhone，Android device，Windows Phone 7．Blackberry．or Kindle．
* Keep your notes：Do you like to keep annotations (注释) and highlights in your eBooks？Don't worry．You can always revisit your notes and highlights through Amazon．com．
How to rent eBooks？
Simply search for the eBook you want to rent on Amazon．com and select the "Rent eBooks" option．After that，a new page will open where you can select how long you’d like to rent the eBook．You can read eBooks for a period of 30 to 360 days．
You decide how long you need the eBook．If you later find out you need it for longer, you can simply extend the time．Or buy it for the normal price whenever you want．
Once you've chosen the time you want to rent the eBook，you simply go to checkout．Or you can use the "Rent now" button．
21. According to the passage，_________
A．eBooks will be changed into other types by Amazon．com
B．eBooks will replace hardcover books in the next few years
C．readers are able to rent eBooks only at Amazon．com now
D．readers get a discount of at least 20% of the normal price
22. To rent an eBook online，which of the following goes last？
A．open a new page B．select the "Rent eBooks" option
C．press "Rent now" button D．choose a rental date
23. The main purpose of the passage is to_________．
A．discuss and assess B．inform and explain
C．compare and evaluate D．describe and argue