Options:
(I). mammals;
(II). rocks;
(III). animals;
(IV). sharks;
(V). a fish;
(VI). cows;
(VII). humans;
(VIII). plants;
Given those answer options, answer the question: Fact 1: Cartilage is a tough tissue that contains a protein called collagen. Fact 2: Sharks have a cartilage skeleton. Given the two facts above, what has skeleton made of tough tissue that contains a protein called collagen?
A:
(IV).