阅读下面短文，从短文后各题所给的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
Language is the most astonishing behavior in the animal kingdom. It is the species-typical behavior that sets humans completely   36   from all other animals. Language is a means of   37   but it is much more than that. Many animals can   38   . The dance of the honeybee communicates the location of flowers   39   other members of the hive (蜂群). But human language permits communication about anything   40   things like unicorns (独角兽) that have never existed. The key   41   in the fact that different words can be   42   together in different ways according to   43   to communicate different meanings.
Language is the most important learning we do. Nothing can   44   humans so much as our ability to communicate abstract   45  whether about the university the mind love dreams or ordering a drink. It is an extremely complex   46   that we take for granted. Indeed we are not aware of most   47   of our speech and understanding. Consider what happens when one person is speaking to   48   . The speaker has to translate thoughts into  49   language. Brain imaging studies suggest that the time from thoughts to the   50   of speech is extremely fast. Only 0.04 seconds! The listener must hear the sounds to   51    what the speaker means. He must use the sounds of speech to   52   the spoken words understand the pattern of   53   of the words (sentences) and finally   54   the meaning. This takes somewhat longer a minimum of about 0.5 seconds. But once started it is of course a(n)    55   process.