What is the purpose of checks and balances and separation of powers in the constitution?

Checks and balances were created in order to ensure that each branches of the government (Executive branch, Legislature, Judicial branch) would be able to fulfill its mandate and also to make sure that no branch becomes more powerful than the other. Meanwhile the separation of power was made in order to make sure that each government branch has a unique role in providing solution for the country. 

your answer should be c, it seems to be the only one that makes sense. mark me branliest : )