单选题：根据以下资料，回答题：Cultural norms so completely surround people，so

根据以下资料，回答题：
Cultural norms so completely surround people，so permeate thought and action，that few people ever recognize the assumptions on which their lives and their sanity rest．As one observer put it，if birds were suddenly endowed with scientific curiosity they might examine many things，but the sky itself would be overlooked as a suitable subject；if fish were to become curious about the world，it would never occur to them to begin by investigating water．For birds and fish would take the sky and sea for granted，unaware of their profound influence because they comprise the medium for every fact．Human beings，in a similar way，occupy a symbolic universe governed by codes that are unconsciously acquired and automatically employed．So much so that they rarely notice that the ways they interpret and talk about events are distinctively different from the ways people conduct their affairs in other cultures．
As long as people remain blind to the sources of their meanings，they are imprisoned within them．These cultural frames of reference are no less confining simply because they cannot be seen or touched．Whether it is an individual neurosis that keeps an individual out of contact with his neighbors，or a collective neurosis that separates neighbors of different cultures，both are forms of blindness that limit what call be experienced and what can be learned from others．
It would seem that everywhere people would desire to break out of the boundaries of their own experiential Worlds. Their ability to react sensitively to a wider spectrum of events and peoples requires an overcoming of such cultural parochialism. But，in fact，few attain this broader vision．Some，of course，have little opportunity for wider cultural experience，though this condition should change as the movement of people accelerates．0thers do not try to widen their experience because they prefer the old and familiar，seek from their affairs only further confirmation of the correctness m their own values．Still others recoil from such experiences because they feel it dangerous to probe too deeply Into me personal or cultural unconscious．Exposure may reveal how tenuous and arbitrary many cultural norms are；such exposure might force people to acquire new bases for interpreting events．And even for me many who do seek actively to enlarge the variety of human beings with whom they are capable of communicating there are still difficulties．
Cultural myopia persists not merely because of inertia and habit，but chiefly because it is so difficult to overcome．One acquires a personality and a culture in childhood，long before he is capable of comprehending either of them. To survive，each person masters the perceptual orientations，cognitive biases，and communicative habits of his own culture. But once mastered，objective assessment of these same processes is awkward since the same mechanisms that are being evaluated must be used in making the evaluations．

The examples of birds and fish____________． A．show that they,t00，have their respective cultures
B．illustrate that human beings are unaware of the cultural codes governing them
C．demonstrate the similarity between man，birds，and fish in their ways of thinking
D．explain humans occupy a symbolic universe as birds and fish occupy the sky and the sea