He conducted a thought experiment to solve a problem in physics.

This is my unused camera.

He is suffering from combat stress reaction.

Pyramid schemes are prohibited by law.

In genetics, linkage disequilibrium is a very important concept.

He joined the multi-level marketing business.

It is reported that North Korea has conducted another underground nuclear test.

He is an expert in experimental psychology.

He is spending a lot of time on experimental research.

He decided to start a multi-level marketing business.