海洋 かいよう 酸素 さんそ事変 じへんじゃなかったです
kaiyōmusansojie nja nakattadesu

Noun
Desu Copula

The polite, past negative form of 海洋無酸素事変

1. It wasn't the oceanic anoxic event.

Past/Perfective
Negative
Polite
Casual Register