According to James Madison, the source of most interest groups or factions is

Answer 1

Are these your choices?

a. the unequal distribution of property.
b. the American political tradition of association.
c. the system of separation of powers in America.
d. the spirit of individualism.
e. the concept of majority rule.

I'll be glad to check your answer.

Answer 2

Yes. I believe it is D.

Answer 3

I disagree.

Read this section on factions.

http://en.wikipedia.org/wiki/Federalist_No._10#The_question_of_faction