It is important to identify the source of infection.

The Proterozoic eon is the longest era in the history of the Earth.

The Eoarchean eon is the oldest era in the history of the Earth.

He was traveling alone in the wilderness.

This cover song maintains the beauty of the original song while adding a new interpretation.

He crossed the snowfield alone.

We have to find out the root of this problem.

He deeply studied the teachings of Buddhism and reached the rank of Hōgen.

Rumors are spreading throughout the town that he is a werewolf.

He is good at learning foreign languages.