PU模式下，无法调节变频器的输出频率大小
A. 对
B. 错
The word “luxury” in paragraph 1 is closest in meaning to ____________.
A. delicious meals
B. chairs with cushions
C. beautifully set tables
D. a condition of great comfort
Which of the following is not true about the first airplanes?
A. They were very cold.
B. Passengers were not allowed to open the windows.
C. Only men were hired to work as flight attendants.
D. They shook so that many passengers got sick.
Which of the following was not the job of flight attendants in the 1920s?
A. To carry passengers’ luggage.
B. To serve the meals.
C. To help the pilot put in fuel.
D. To help passengers who felt sick.
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