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
为什么有一题中debate+ over+whether从句，这题中却没有，到底是怎么样的啊？请赐教，呵呵
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