Research studies that retest the same group of people throughout their lives are classified as studies.

i believe that the answer to the question provided above is that the role of campaign committees is to act as a bridge between state and local campaigns.

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.