Airplanes are used to carry passengers, cargo and mail. Air transport companies operate scheduled airlines and non-scheduled services over local, regional, national, and international routes. The aircraft operated by these companies range from small single-engine planes to large multiengine jet transports.
The first air passenger services began in 1910, when dirigibles began operation between several German cities. The first scheduled airplane service to carry passengers began in the U.S in 1914. Several experimental airmail flights took place in India, Europe, and the United States before World War I, but air transport service did not become a true business until after the war.
During World War Two, intercontinental air transport became firmly established. After the war the new long-distance transports with advanced facilities were increasingly able to avoid storms and strong wind and make flights more economical and consistent. A new generation of "jumbo-jet" transports began operations in 1970, and the supersonic transport entered passenger service in 1976.
练习:
1. Paragraph 2__________.
2. Paragraph 3__________.
3. Paragraph 4__________.
4. Paragraph 5__________.
A Necessity for developing adult education
B Early days of adult education
C Ways of receiving adult education
D Growth of adult education
E Institutions of adult education
F Definition of adult education
5. Some adults want to learn _______________.
6. There are various forms of adult education, including ____________.
7. Adult education has been made necessary ___________.
8. The earliest organized adult education _______________.
A by social and economic changes
B guided self-study and correspondence courses
C by studying together with children
D what they did not manage to learn earlier
E dates back to the eighteenth century
F mass production