America is becoming a nation of book lovers— notebooks, netbooks and smartbooks;  that is, if you believe the computer manufactures.
Notebooks
Notebooks, the senior citizens of mobile computing, are slimmed-down laptops. A notebook is an extremely lightweight PC, typically weighing less than 6 pounds and often compact enough to fit easily into a briefcase(公文包）. Aside from portability (轻便）and size, the biggest difference between a notebook computer and a desktop PC is the display screen. In terms of computing power, modern notebook computers are nearly equal to PCs.
Netbooks
The weight of a notebook can cause a lot of wear and tear on the shoulders, which is one reason why mobile workers joined the netbooks land rush. Also called mini notebooks, ultra portables or sub- notebooks, these small, light and inexpensive lap-top computers are used for general computing and for access to web-based applications.
When first introduced, netbooks featured smaller screens and keyboards, often had reduced specification and computing power, and lacked key features, such as optical drives (光驱）. They've since grown in size and features, often confusing the distinction between a netbook and notebook computer.
A netbook's display typically ranges from 7 to 10 inches. It weighs less than 3 pounds, and sup-ports a keyboard that is reduced in size. Netbooks have built-in WiFi, Ethernet, USB ports and slots (扁口）for flash memory cards. To keep them small and compact, netbooks do not have a CD or
DVD drive, and many use solid-state flash drives in-stead of hard drives for storage. Flash drives have no moving parts so they're less likely to break, and are smaller than regular hard drives, which saves space and weight.
Smartbooks
Smartbooks are the newest book on the block. Smartbooks combine the features of both a smart- phone and a netbook computer in a device that's mobile like a phone, yet comes in a laptop-style body with a screen that's 5 to 10 inches in size. Other features include long battery life，3G connectivity and GPS capability. And it has long battery life，8 to 12 hours.
Smartbooks are for the group who like multimedia and social networking, and have real-time information flow.
What do we know about a notebook?

A．It can serve as a briefcase.

B．It may cause pain in your shoulders.

C．It has as big a display screen as PCs.

D．It can deal with calculation as well as PCs.

A netbook does NOT have __________

A．a hard drive

B．a USB slot

C．a flash drive

D．a keyboard

Which of the following is a smart book?

The purpose of writing this passage is to __________

A．prove how Americans love books now

B．advertise several new kinds of books

C．introduce some mobile computing devices

D．explain the development of computers