Final answer:
The correct answer is option C) Compartan sus coches con amigos.
Step-by-step explanation:
The correct answer is option C) Compartan sus coches con amigos. This sentence translates to 'Share your cars with friends' which is a formal, plural (ustedes) command for an environmental publicity campaign to protect the environment. It is important to use the plural form of the verb 'compartir' (to share) and the possessive pronoun 'sus' (your) to address a group of people.