Answer :
If you saw the sign that states "Save the planet - don't litter" the technique of policy enactment being used is hortatory. This is because they are strongly urging you not to litter.
The correct option is:
Horatory.
In terms of policy implementation, hortatory techniques are those that encourage people to comply with a policy by appealing to their better senses in an attempt to make them act in a certain desired way.
This is a technique most useful in public campaigns, such as one to discourage smoking or drinking.