Select from the following.
(1). adult giraffes;
(2). adult sea squirts;
(3). gastropod shells;
(4). adult starfish;
(5). Leptospirosis;
(6). adult sloths;
(7). Veins and arteries.;
(8). the body's largest organ;

You are presented with the quiz "What are barrel-shaped?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "adult tunicates are barrel-shaped" and "sea squirts are the best known tunicates". So, what's the best answer to the question?
Answer:
(2).