He is an expert in public law.

This antigen triggers a specific immune response.

This tank has strong armor.

He was clad in armor all over his body.

This vaccine contains the antigen of the new coronavirus.

He took a train to Tokyo in the allative case.

A binary operator is one of the basic concepts in algebra.

This trumpet is made of brass.

I decided to start a new business taking advantage of this favorable opportunity.

The janitor is cleaning the classroom.