His behavior was very polite.

I haven't paid this year's tax yet.

His advice was completely useless.

Astatine is one of the halogen elements.

I play table tennis with my friends every weekend.

He ate ramen while standing.

Standing and eating soba noodle shops are convenient dining places for busy people.

Even though three years have passed, I can't forget him.

The sea otter is a rare animal, and its ecology is not well known.

The sea otter is a very rare animal.