An obligate anaerobe is an organism that would die in an oxygenated environment. What could be assumed about these organisms?

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

carbon traps heat so more of it makes it hotter causing global warming. during the ice age carbon levels in the atmosphere were low so it got very cold. so the common things between them is carbon levels in the atmosphere.