The role that weather plays in formation flight has not yet been clearly defined.
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It has been documented that during World War II, America's armed forces once tried formation flight to save fuel.
A. Right
B. Wrong
The upwash experience may save propelling energy as well as reducing resistance.
A. Right
B. Wrong
Which of the following does NOT belong to products that help create people's habits?
A. Tide
B. Crest
Colgate
D. Unilever
The author's attitude toward the influence of advertisement on people's habits is______.
A. indifferent
B. negative
C. positive
D. biased