Many features similar to those aeronautical innovations developed by man can be observed a

mongst birds, insects and plants. At times, observations of these natural phenomena have inspired man to imitate nature and modify existing designs. At other times, the natural example has only been recognized well after great amounts of time and valuable materials have been devoted to refining a similar human invention.

Birds deserve credit not merely for demonstrating flight was possible, but for providing templates for the shape of aircraft wings. The wings of birds suggested the pattern for leadingedge wing slots that improve ascent at slow speeds and for conical cambered wingtips that increase lift and stability. Other characteristics of bird wings, such as a trailing edge flap to aid in smooth landings, were not recognized as important until they had been designed independently by aeronautical engineers. Considerable research effort in aeronautics could probably have been saved by more thorough analysis of bird flight.

The insect world has also contributed significant ideas in the realms of navigation and guidance. In order to aid airline navigation during take-offs and landings under adverse weather conditions, engineers developed a system for locating the sun when it was hidden by clouds through observing polarized light—light which travels in a single direction. The research was instigated(鼓励,激发)after studies of honey bees demonstrated that they used this mechanism to determine their location when the sky was darkened. In another credit to the insect world, the evasive guidance systems of certain missiles use angular acceleration detectors modeled after the multi-lensed eyes of houseflies which amplify subtle movements by splitting images into a mosaic(马赛克)resembling a large display of televisions tuned to the same channel.

Even entities which never take flight themselves are responsible for guiding the hand of aeronautical engineers. The winged seed of a palm tree was the model for an early glider, and the single-winged, autorotating maple seed was the prototype for a means of air-dropping cargo by parachute.

The author argues that money for aeronautical research money could be invested more efficiently if______.

A．more advanced products were used in airplanes

B．more research was devoted to studying bird flight

C．greater efforts were directed towards shape designs of aircraft wings

D．greater emphasis was put on guidance systems