Why did voter participation in elections increase dramatically between

Why did voter participation in elections increase dramatically between 1824 and 1840?

a. The population of the United States grew, so the number of voters increased.
b. People who had been migrating were settled and could register and vote.
c. African Americans in the North were given permission and encouragement to vote.
d. Politicians changed campaigning practices, drawing in more voters.
e. Native Americans in the South and West were given permission and encouragement to vote.

ANSWER
D