The decline of the Greek aristocracy's power in the sixth century B.C. was the result of ______.

A．to define the term social class does not involve much difficulty
B．there is much alternation in people's social classes
C．to evaluate a person's social class is a very complex procedure
D．we can tell which social class a person belongs to by the way he behaves

A．Slaves in Greece in the sixth century
B．
C．were not politically significant.B. The "burghers" of the later Middle Ages constituted an entirely new social class.C. To some extent, social mobility can be attributed to the growth of trade.
D．The new class made up of traders and executive officials of the later Middle Ages made the development of a money economy possibl