How did people get from place to place during the 1920s?

In the 1920's, trains and ocean liners were the dominant mass transportation methods, providing comfortable, reliable transport to millions of American vacationers. Trains had opened up the continent and ships the world, but newer methods of transport captured the imagination of the public and reduced travel times.

Explanation:

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.  

speak engilish and i could have an answer