The correct answer is C) they are less harmful to sea life than lighter oils. Heavy fuel oils, also known as bunker oils, are typically more viscous and less volatile than lighter refined oils. When spilled, heavy fuel oils tend to be less harmful to marine life because they do not spread as easily and do not readily penetrate sensitive habitats like coastal areas. Additionally, the thicker consistency of heavy oils can make them easier to contain and clean up compared to lighter, more fluid oils which can rapidly disperse. The other options are incorrect because heavy fuel oils are generally considered less toxic and damaging to sea life compared to lighter refined petroleum products.