The law has a great many rules, showing when and how far a man is to be punished, or if he should be made to hand over money or property to his neighbors, and so on. These rules are contained in books. A lawyer learns them mainly by reading books. He begins by doing little else than reading, and after he has prepared himself by three years' study, still, he has to, almost every day, read more about some new questions which he has to answer. The power to use books, then, is a special skill which a would-be lawyer ought to possess. He ought to have enough flexibility to make it easy for him to collect ideas from printed words. He ought to have some readiness to find what a book contains, and something of an instinct for where to look for what he wants. But although this is the power which he will first feel in need of, it is not the most important. A lawyer does not study law to recite it; he studies it to use it and act upon the rules which he has learned in real life. His business is to try cases in court and to advise people what to do in order to keep out or get out of trouble. According to the passage, a good lawyer should know how to   _  .
understand and use what he reads be effective in everything collect ideas from different sources be effective in court