In the past few years, personal computers （PCs) have become better, stronger and faster bu

In the past few years, personal computers (PCs) have become better, stronger and faster but so have the bits and pieces you plug into them.

Monitors

If big is better when it comes to screens or monitors, it is also more costly. As with big TVs, big computer screens are expensive. The Americans' touching devotion to imperial measurements still holds in the computer industry, so people still shop for goods by the inch rather than by the centimeter.

Anyone planning to do any desktop publishing with a PC will want a larger screen; increasingly, however, World Wide Web users and game players are also discovering the rewards of a larger monitor.

American medical television series, such as ER, regularly show the hi-technology used in modern US hospitals. A good example is the thin flat screens used on all computers. Know why they have thin, flat monitors？ Because they're LCD, which is less bulky and smaller than the standard CRT, the kind used in television sets. The LCD screens don' t emit any electromagnetic radiation, which could interfere with the heart machines and other sophisticated electronic equipment in hospitals and thereby cause a crisis. LCD screens are lighter, flatter and throw out less heat than CRTs. They are also at least three times the price — and, as such, out of the league of home users.

Scanners

A scanner is a device a bit like a photocopier, which creates a digital image of a page and stores it on disk. These days most scanners handle color images and are beginning to come in quite a variety of shapes and sizes. The scanner market is a great example of the way the ground can shift in peripherals. Scanners used to be expensive pieces of professional equipment; now, they are an increasingly useful addition to the home or small business PC environment.

The most practical home scanners used to be hand-held devices that the user could slowly track across the desired image, strip by strip. Now, however, there is a wide range of both flatbed and sheet-fed scanners available between ＄ 500 and ＄ 1200.

The first application for scanners has been to scan images or photographs, especially for reproduction in publications. Besides scanning images, the other major application for scanners is OCR scanning in printed articles and converting them to text on the PC.

Printers

There are three main types of printers—dot matrix, inkjet and laser. Dot matrix models still have their place in high-volume commercial jobs, but few home and small office users choose them now. They might be cheap, but they are noisy and the results (especially in color) simply aren't very good.

By contrast, inkjet printers have taken the consumer market by storm in recent years. Unlike dot-matrix printers, which hammer pins against a ribbon as a typewriter does, inkjets silently squirt ink onto the page.

Inkjets, however, are slow, and the quality of their printed type isn't as crisp as you want for professional use. So the next step up is a laser printer. Since the introduction of GDI technology—which cuts down the demands on the printer hardware by getting the PC to do the hard work of the printing process—laser printers have come down markedly in price.

Color laser printers are a bit like color laser copiers—they exist, but only in larger offices and specialist graphics businesses. The various kinds of color laser will inevitably get cheaper—but they may be overtaken in the consumer market by new printers on the US market, which turn out glossy prints which look like photographs and are aimed at users of the new computerized, digital cameras.

This passage is most likely extracted from ______.

A．an advertisement on PCs

B．a primary school textbook on science

C．an article introducing the latest developments in the computer world

D．a research paper on the functioning of the computer