阅读下列短文，从每题所给的四个选项(A、B、C、和D)中，选出最佳选项，并在答题卡上将该项涂黑。
A
CDL Certification Guide
What is CDL?
A CDL or commercial driver's license is required to operate large vehicles intended for use by a company or an organization. Because operating large commercial vehicles requires more specific skills than driving a small personal car, a specialized license indicates that you have completed the proper training to be safe and efficient.
If you are interested in becoming a truck driver, or a school bus driver or operating other large vehicles for your career, you will likely need to obtain a CDL before you are qualified to get the job.
Types of commercial driver's licenses
There are three main CDI, classifications: Class A. Class B and Class C. The classification for your CDL will be dependent upon factors such as the vehicle's weight, purpose and skills required to properly operate it.
Jobs that typically require a CDL
Jobs that involve transporting people, materials and products are crucial to maintain a healthy economy. If you have strong driving skills and the desire to be behind the wheel instead of behind a desk, a driving job might be a good fit for you. A CDL endorsement(违章记录)is a certification or confirmation of a highly specialized skill. Here are just a few examples of driving jobs that might be a good fit for you.
* School bus driver
CDL requirement: Class A or Class B + School bus(S) endorsement.
National average salary: US $ 29, 915 per year
* Truck driver
CDIL requirement: Class A or Class C
National average salary: US $ 71.720 per year
* Hazardous(危险的)materials driver
CDL requirement: Class A, B or C + Hazardous materials(H)endorsement
National average salary: US $ 87,466 per year
* Van driver
CDL requirement: Class A + Passenger(P) endorsement
National average salary: US $ 105, 604 per year
21. What can we know about CDI, from the text?
A. It is needed when one drives a private car.
B. It is provided by a college or a university.
C. It recognizes someone's specific skills in driving.
D. It offers drivers proper training before getting a job.
22. Which of the following determines a CDL's classification?
A. The driver's age and character. B. The vehicle's weight and purpose.
C. The vehicle's speed and condition. D. The driver's experience and driving years.
23. What is the national average salarly of a van driver?
A. US $ 29, 915. B. US $ 71, 720. C. US $ 87, 466. D. US $ 105, 604.
