Which of the following does the writer explain?

D
细节题。第三段最后一句指出“This macabre scenario may help solve several sea mysteries, such as why fishermen report seeing “fish walks” （fish trying to leave the water）…”，该句括号里的内容是对“fish walks”的解释，由此可知“fish walks”的原因是被这些微生物麻痹了神经，从而呼吸困难。因此选D。