放射 ほうしゃ せい崩壊 ほうかい系列 けいれつでしょう
hōshaseihōkaikeiretsudeshō

Noun
Desu Copula

Expresses probability in a polite manner ("probably…") of 放射性崩壊系列

1. Probably a radioactive decay series.

Polite
Presumptive
Conjecture
Physics