A major chemical spill occurred five years ago at Baker’s Beach, the world’s sole nesting ground for Merrick sea turtles, and prevented nearly all the eggs laid that year from hatching. Yet the number of adult female Merricks returning to lay their eggs at Baker’s Beach has actually increased somewhat since five years ago. Clearly, environmentalists’ prediction that the world’s Merrick population would decline as a result of the spill has proven unfounded.

Which of the following, if true, most seriously undermines the argument offered in refutation of the environmentalists’ prediction?

A. The chemical spill five years ago occurred at a time when there were neither Merrick sea turtles nor Merrick sea turtle eggs on Baker’s Beach.
B. Female Merrick sea turtles begin returning to Baker’s Beach to lay their eggs when they are ten years old.
C. Under normal conditions, only a small proportion of hatchling female Merrick sea turtles survive in the ocean until adulthood and return to lay their eggs at Baker’s Beach.
D. Environmental pressures unrelated to the chemical spill have caused a significant decline in the population of one of the several species of sea birds that prey on Merrick sea turtle eggs.
E. After the chemical spill, an environmental group rejected a proposal to increase the Merrick sea turtle population by transferring eggs from Baker’s Beach to nearby beaches that had not been affected by the spill.

I feel D here. A seems totally unrelated to the argument

I marked B by PoE but I was confused b/w B and C.

Any expert view on this question?
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I thought the answer is B.

Because a chemical spill occurred five years ago and turtles are returning to lay eggs on the beach, we can conclude that turtle population is unaffected by the spill.

If it takes 10 years to get to maturity and return to the beach to lay eggs, then turtles unaffected by the spill would return. Therefore, the environmentalist's drawn conclusion could still be true.