What was the reason for the split between Shia and Sunni Muslims?

Shias believed that the next leader should come from Muhhammed's family, but Sunnis believed that the next leader should be chosen by the community.

Explanation:

the answer to fill in the blank in this question would be the word resource, it is defined as the money, material or people (since human resource is a very valuable good) that a company or a person has at disposition (meaning they can use the resource as they see fit), to be able to complete a task or achieve a goal.