Other Things Equal, Which of the Following Would Shift an Economy's

Multiple Choice

Other things equal, which of the following would shift an economy's production possibilities curve to the left?

A) the discovery of a low-cost means of generating and storing solar energy
B) the entrance of more women into the labor force
C) a law requiring mandatory retirement from the labor force at age 55
D) an increase in the proportion of total output that consists of capital or investment goods