Why did native americans develop different cultures?

Constant warfare among the different Native American groups led to cultural differences.

Let's look at the options:

A. The different cultures were established in Asia and carried into the Americas.
This is not very likely, as the cultures would have changed too much in the time of the migration

 B. Constant warfare among the different Native American groups led to cultural differences. 
Warfare does not necessarily lead to differences, it is possible to have a comflict with people of the same or similar culture

C. The cultures developed to suit the local climate and available resources. 
I think that this is the best answer. Climate and resources often influence cultures. 

D. Native American leaders decided differences would help identify members of their own tribes. 
Cultures are too big for single people to control them, so not

An elector in the electoral college.