Read the sentence.
ancient remains are making the normally flat land hilly.
what kind of complement is indicated by the bolded word?
object complement
predicate nominative
direct object
predicate adjective

The correct answer is "object complement", because it follows a direct object (in this case "the normally flat land") and renames it or states what it has become. It cannot be "predicative nominative" because "hilly" is not a noun, "direct object" here is "the normally flat land", and a predicate adjective follows a linking verb (for example, She is PRETTY.) So the only option left is "object complement".