In August 2012,the Official U-3 Unemployment Rate Dropped from 8

In August 2012,the official U-3 unemployment rate dropped from 8.3 percent to 8.1 percent. This change could have been caused by

A) unemployed workers giving up looking for a job.
B) part-time workers getting a full-time job.
C) full-time workers becoming part-time workers.
D) workers who had previously given up looking for a job starting to look again.