致死 ちし突然 とつぜん変異 へんいじゃなかったです
chishitotsuzenhen'ijanakattadesu

Noun
Desu Copula

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

1. Wasn't fatal sudden mutation.; Wasn't a fatal, sudden change.

Past/Perfective
Negative
Polite
Casual Register