What are the formal sources of law in the Roman Republic?

I - The law was a provision dictated by the people when they met in comitia.
II - The law is what the Roman people establish at the proposal of a magistrate.
III - The law can be divided into curiadas and centuriadas.
IV - The Praescriptio is the most important part of the law.
a) Only I and II are correct.
b) Only II and III are correct.
c) Only III and IV are correct.
d) All statements are correct.