Density is a measure of select one:
a. the amount of weight in an object. incorrect
b. the mass per volume of an object.
c. the size of an object.
d. the hardness of an object

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.  

answer; size, shape, color and status;