To be able to answer this question, we first need to understand what transitive and intransitive verbs are. A transitive verb is the one that directly affects an object, for example, the dog runs to the forest. Run, is a transitive verb because it is affecting the object directly, which would be forest. In contrast, intrasitive verbs are the ones that do not directly affect the object being used, like for example: The dog always runs. In this last case, there is no direct object to affect, which ,transforms this verb into an intransitive one. In the case of the question, it would be a transitive verb because set is affecting the direct object, which is hills.