The 30′s were not less invention-intensive bringing us the jet engine, helicopter, tea bags, sticky tape, ballpoint pen and the first photocopier.
30年代人们也有不少发明，如喷气发动机、直升机、泡茶袋、胶带、圆珠笔和第一台复印机。
Innovation in aviation has centered on the development of the jet engine for civil use, first in a turbo propeller form and later as a pure jet.
航空业的革新集中于民用航空喷气式发动机的研发，首先是涡轮螺旋桨发动机，后来是纯粹的喷气机。
Variable. This variable is defined by the JET engine.
该变量是由JET引擎定义的。
Variable. This variable is defined by the JET engine.
该变量是由JET引擎定义的。
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