From September 2013 to September 2014, the Employment-To-Population Ratio Increased

From September 2013 to September 2014, the employment-to-population ratio increased from 58.6 percent to 59.0 percent. This change could have been the result of

A) a decrease in the working-age population.
B) unemployed workers becoming part-time workers.
C) unemployed workers becoming discouraged workers.
D) discouraged workers starting to look for jobs again.