What was the most important effect of isolationism on China during the Qing dynasty?

C: 4 stops . You can tell this by reading the graph, find where 13 is on the y-axis (the left side going up) to find number of passengers and then go across to find how many stops for 13 passengers. In this case you have to read whats not on the graph and realize that 13 passengers is between the 12 and 16 points, a quarter of the way up