Mustard gas is a type of chemical weapon and is very dangerous.

It seems that the exhaust valve of this engine is broken.

The engine displacement of this car is 2000cc.

The exhaust pipe of my car has broken.

It took a long time to set up the development environment.

We must strive to protect the natural environment.

We should recycle to prevent environmental pollution.

We need to solve the problem in the production environment.

He is traveling around the world as an ecologist.

Fergus is my best friend.