He is the main organizer of this event.

He is a world-renowned researcher.

This area is off-limits due to high radiation levels.

We have achieved an important milestone in this project.

Who is the author of this book?

On cold days, a heater is necessary.

Hydrocarbons are fundamental components of organic chemistry.

The wheel of my bicycle has gone flat.

Lithium hydride plays an important role in chemical reactions.

Hydrogen peroxide is often used for disinfecting wounds.