The study of nekton is an important part of marine biology.

My biological clock is disrupted, and I've been having sleepless nights.

Invasive species can have a major impact on the natural environment.

The first day of the month is the beginning of a new month.

I have been to France once.

His first choice of school is the University of Tokyo.

I went to see a movie by myself.

He has a competitive spirit that does not allow even one defeat.

He finished all his work all at once.

Watching a movie alone is enjoyable.