In the context of mathematical functions, what are the two ways of defining a function?

I - Through tables that explicitly register the value of the dependent variable for each value of the independent variable.
II - Through graphs that show the relationship between variables.
III - Through formulas that relate the dependent variable to the independent variable.
IV - Through a combination of tables and graphs.
a) I and II are correct.
b) II and III are correct.
c) I and III are correct.
d) I, II, and III are correct.