I often eat alone.

I am enjoying eating alone.

He showed his true colors under difficult circumstances.

We should always remember the power of Kannon in difficult times.

Chrysophyta are living in this pond.

Chrysophyta perform photosynthesis underwater, supplying oxygen.

I went to see the beautiful scenery of the Han River.

He is working as a member of the International Criminal Police Organization.

He holds a very high position in that company.

What is the common difference of this arithmetic sequence?