致死 ちし突然 とつぜん変異 へんいではありませんでした
chishitotsuzenhen'idewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 致死突然変異

1. Was not fatal sudden change.; Was not a fatal sudden mutation.

Past/Perfective
Negative
Polite
Formal Register