Which of the following purposes do you think political parties serve?
a. they use the funds from the federal budget for personal gains
b. they make it more hard to decide who or what to vote for
c. they assist in the decision-making process
d. they divide and separate a lot of different people who ave similar views

Let's look at all the options:

A. they use the funds from the federal budget for personal gains
-no, they're not allowed to use it for personal gains

B. they make it more hard to decide who or what to vote for
-no, this is not desired: they should make the voting easier by presenting their opinions on issues

C. they assist in the decision-making process
-I think that this is the best answer. The decision here is the political decisions and administrative decisions in a country.

D. they divide and separate a lot of different people who ave similar views
-no, rather they unite people with similar views.

C. High population densities made it easier for diseases to spread