加快城市群建设,实施城市群发展规划,优化提升()、()和()三大城市群。
A. 北上广
B. 长三角
C. 珠三角
D. 京津冀
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长期以来,我国一直采取大力发展大城市,形成城市群以带动周边城市的发展模型。()
A. 对
B. 错
Who is Sir George Cayley?
A. Pioneer in aviation
B. Famous theorist
What are the four forces identified by Cayley?
A. weight
B. drag
C. lift
D. thrust
Who is Charles Green
A. a politician
B. a balloonist