A good reader is very much like a driver. He must change his reading speed to fit his purpose and the material he is reading, just as a driver does to fit the road situation (情况). A good reader may be able to read a thousand words per minute (WPM), but he won't use that speed for everything he reads. A good reader doing research (研究) reading in the library may read at the speed of 1,000 words per minute as he looks for materials for a report. But once he finds something that is useful to him he may need to slow down to 100 WPM. A good reader may read newspaper and magazine articles at 600 WPM, but it may take him 150 WPM to read his science or maths text. A driver has a wide change of speed, so has a good reader. According to the writer, good readers can ______ .