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

We wrote essays for peer grading.

He works at the switchboard.

We write in the exchange diary every day.

In mathematics, the commutative law applies to addition and multiplication.

Let's exchange keys tomorrow.

Fergus is my best friend.

This factory has significantly reduced its carbon dioxide emissions.

Fougasse is one of my favorite types of bread.

The police used tear gas against the demonstrators.