During the 1920s, the U.S. economy A. stagnated.
B. fluctuated constantly.
C. enjoyed prosperity.
D. saw some regions enjoy prosperity while others suffered deeply.

the correct answer is C

Explanation:

When we express that the scale is 1:30 we mean that the objects of the realization are reduced by a factor of 30 in the graph, for example a distance of 30 cm in the graph is represented by a distance of 1 cm.

Therefore something that in the graph has n value to bring it to real size must be multiplied by the scale.

Applying this to our case if there is

               10 boulder on the chart

in reality there are #_boulder = 10 30

                                #_boulder = 300 boulder

so the correct answer is C