What role do themes play in historians' efforts to organize information about the past?
a. they historians decide whether or not a primary source is credible .
b. they make it possible for historians to gain a deep understanding of a particular region .
c. they historians focus on the effects of one important idea on different societies over time.
d. they allow historians to better understand how earlier historians interpreted past events .

The original tragedy of the commons concerned grazing cows and sheep in fourteenth century england. choose the statement about this tragedy of the commons that is correct. a. the tragedy of the commons in fourteenth century england was overcome by the common lands being enclosed and privatized. b. everyone had an incentive to ensure that the land was not over grazed. c. even with the tragedy of the commons, the use of the commons was efficient. d. the tragedy of the commons in fourteenth century england was overcome by falling wool prices and the decrease in the size of sheep flocks.