He is studying the major ethnic groups in that region.

This species has different characteristics depending on its subgroup.

Finding an asterism is a great joy for astronomers.

Looking down at the sea, I could see a school of fish swimming.

Please choose the correct one from the set of possible answers to this question.

It's very exciting to see a crowd of horses running at the racetrack.

A new approach is needed to solve this set of problems.

This colony is forming a unique ecosystem.

A meteor shower appeared in the night sky.

He was diagnosed with Asperger's syndrome.