There are all together ____(how many) arched stone bridges spanning over the Outer Golden Water River. According to the historical records, the middle bridge was for the emperor only, so it was called the ____(御路桥).The two bridges on each side were used by the royal family members and therefore, they were called____(王公桥).The two bridges farther out were the Ministerial Bridges(品级桥) for the ____above the third rank.The remaining two bridges were for the officials below the fourth rank, so they were callcd the ____(公生桥).