题目选项分析

The rise of the Incan empire rested not only on the Incas' military might and the ability of their rulers but also on their imposition of a highly organized economic and political system on many different ethnic groups, who were permitted to retain many of their customs and often their own leaders.

The rise of the Incan empire rested not only on the Incas' military might and the ability of their rulers but also because of their imposition of a highly organized economic and political system on many different ethnic groups, who they permitted to retain many of their customs and often their own leaders.