Read the following passage:
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“When a clear understanding had been obtained, there was no difficulty in designing suitable propellers, with proper diameter, pitch, and area of blade, to meet the requirements of the flyer.”
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Select the best summary of this information.

A. The inventers designed propellers with all the correct dimensions for the flyer.

B. The flyers required constant adjustments.

C.The inventors applied what they learned to create better parts.

D.The flyers needed to be better understood in order to continue making it better.