What are fatty acids?

I- They are monocarboxylic acids of linear chain R-COOH, where R is an alkyl chain formed only by carbon and hydrogen atoms.
II- They can have a chain length between 4 and 24 carbon atoms.
III- The carbon chain can be saturated or unsaturated.
IV- The most abundant fatty acids in nature are oleic acid and palmitic acid.
a) I and II are correct.
b) II and III are correct.
c) I, II, and IV are correct.
d) II, III, and IV are correct.