Fill in the blank with the correct collocation.

Motorists committing this infraction are _________ fined.

heavily

The correct collocation to fill in the blank is heavily fined.

The word "heavily" means in a large amount or to a great extent. It is the most appropriate option in this context because it conveys the idea that motorists who commit this infraction will be fined a large amount of money.

The other options are incorrect.

• "Wholly" means completely or entirely. It does not make sense to say that motorists who commit this infraction are wholly fined.
• "Hardly" means scarcely or barely. It does not make sense to say that motorists who commit this infraction are hardly fined.
• "Slowly" means at a slow pace. It does not make sense to say that motorists who commit this infraction are slowly fined.