The following chart shows the population of Europe from 1750 to 2000. Use the chart to answer the following question:

Look at the data in the chart. What developments in mid-17th century Europe help explain this data? (5 points)

a. Population increased in the mid-17th century because all European nations united under a common empire.

b. Population decreased in the mid-17th century because most political systems were unstable.

c. Population increased in the mid-17th century because there was more religious tolerance after the Thirty Years' War.

d. Population stayed the same in the mid-17th century because immigration and emigration rates were equal.