What was the main idea of the Monroe doctrine

It was a warning for European countries to stop colonization in the western hemisphere. (b)

Explanation:

President James Monroe wanted Europe to stop trying to colonize the western hemisphere and was even going to force them to stop this, thus creating the Monroe Doctrine, stating that Europe could not colonize the west. Good luck ◕‿◕

even though you have attached neither the chart nor the generalizations, i have located them online. the right answer is d, since they are asking you about a generalization. you can only infer from the chart that between 2008 and 2009 the number of employed workers decreased significantly (from over 115 millions to 107 millions approximately), which signals some type of economic crisis.