Answer:
a. rises but real GDP per person falls
Step-by-step explanation:
Gross domestic product is the total monetary value of output that is produced by an economy in a given period.
GDP increases as the income increases. This is because people have more money to spend on goods and services.
So if people are retiring they will earn pension that will be spent. This increases productivity of the economy.
However since the number of people working is reducing there will be a reduction in real GDP per person. Only few people are producing and output will be allocated to a large population many of whom are not working.