In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").

Remora fish (A) attach themselves to boats like barnacles (B) act as a support system during a shark's reproduction cycle (C) are exclusively kelp and seaweed eaters (D) act as a clean up crew for a shark's crumbs
D