单项选择题

The great chariot of society, which for so long had run down the gentle slope of tradition, now found itself powered by an internal combustion engine. Transactions and gain 51 a new and startling 52 force.
What forces could have been 53 powerful to smash a comfortable and 54 world and institute in its place this new society There was no single massive 55 . It was not great events, single adventures, individual laws, or charming 56 which 57 about the economic revolution. It was a process of internal growth.
First, there was the gradual emergence of national political 58 in Europe. A second great current of change was to be found in the slow decay of the religious spirit under the 59 of the skeptical, inquiring, humanist views of the Italian Renaissance. Still another 60 current lies in the slow social changes that eventually rendered the market system possible. In the course of this change, power naturally began to gravitate into the hands of those who understood money matters--the merchants.
A. issues B. events C. situations D. incidents