The equilibrium length of this spring is 5 centimeters.

He prefers natural foods.

This wood may spontaneously combust if the humidity is high.

His car spontaneously combusted all of a sudden.

Natural rights are rights that humans have from birth.

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

He is an expert in parasitology and conducts many researches.

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.