What is the difference between positive economics and normative economics?

I. Positive economics seeks objective explanations of the functioning of economic phenomena.
II. Normative economics offers prescriptions for action based on value judgments about what is good or desirable.
III. Positive economics indicates whether a certain event is good, desirable, or convenient.
IV. Normative economics is limited to observing economic facts, studying their causes, and evaluating their consequences.
a. I and II are correct.
b. II and III are correct.
c. I and III are correct.
d. I and IV are correct.