Answer:
No contaminar el río porque es de todos.
Step-by-step explanation:
A command that could help people of Melo to fix the problem in the river could be the following:
Do not pollute the river because It belongs to everyone.
In Spanish the command would be translated like this:
"No contaminar el río porque es de todos."
Other ways to say it could be:
"No contamines el río porque es nuestro."
"No contamines el río porque nos pertenece."