What is the main function of banks in the economy?

I - To receive money from the public and use it to grant loans.
II - To concentrate dispersed capital and form large capitals.
III - To create primary money through credit operations.
IV - To provide security for valuable things and money storage.
a) Only I and II are correct.
b) Only II and III are correct.
c) Only I, II, and III are correct.
d) Only I, II, III, and IV are correct.