单选题 Bus drivers must have a commercial (商业的) driver’s license (CDL). This can sometimes be earned during on-the-job training. They must possess a clean driving record and may be required to pass a background check. They also must meet physical, hearing and vision (视力) requirements. In addition, bus drivers often need a high school diploma or the equivalent. Bus Driver Training Bus drivers typically go through 1 to 3 months of training, but those who already possess a CDL may have a shorter training period. Part of the training is spent on a driving course, where drivers practice various skills with a bus. They then begin to drive in light traffic and finally make practice runs on the type of route that they expect to drive. New drivers make regularly scheduled trips with passengers and are accompanied (陪伴) by an experienced driver who gives helpful tips, answers questions, and grades the new driver’s performance. Some drivers’ training is also spent in the classroom. They learn their company’s rules and regulations, traffic laws, and safe driving practices. Drivers also learn about schedules and bus routes, fares, and how to communicate with passengers.《问题》：The passage is mainly about how to________.