请教语法大全中一道题

14.   A little under a million years ago, the briny waters of the Baltic Sea began flooding into the cold North Atlantic: geologists are still debating whether the flood was gradual or created a cataclysm.

(A) whether the flood was gradual or created a cataclysm

(B) if the flood was gradual or created a cataclysm

(C) about whether the flood was gradual or cataclysmic

(D) whether the flood was gradual or cataclysmic（D）

(E) whether the flood was gradual or it created a cataclysm

为何是D不是A？

从语法上gradual 与cataclysmic不对称，而was gradual or created a cataclysm是对称的，从语义上，大水不是灾祸而是引起了灾祸，是不是因为created动作发出者必须是人？但牛津字典里有用抽象名词做主语的例句。请NN指点

gradual 与cataclysmic是对称的，因为它们都是形容词，组成系表结构。

如果用被动语态，be created，那么就表示flood是被人创造的，显然水灾是自然发生的，因此不能用被动语态。