Please explain D

@msaber, Happy to help. We're looking to weaken the scientist's hypothesis. With causal arguments, the missing piece between the premises and the conclusion of the argument is that the correlation does not definitively imply causation. It's possible there's an alternative cause for the effect, or maybe the argument is confusing the cause and effect with one another. In the correct answer, we know that we need to see an alternative cause, cause without an effect, or effect without a cause in the answer choice. The correct answer choice will be the one that makes the argument's conclusion less likely. (D) says, "Sediment from the ocean floor near Antarctica reflects no increase, during the last ice age, in the rate at which the shells that diatoms leave when they die accumulated." (D) is capturing effect without a cause. The effect (the increase in carbon dioxide) occurred, but the cause (the increase in algae) didn't. This undermines the scientist's hypothesis, so it's the correct answer. Hope this helps. Let us know if you have any more questions!