Don't understand this question.....can someone plz help?

I would say that each of the 6 sentences is relevant or provides usable information explaining why the Italian peninsula was a desired location for settlement in ancient times. The sentence (#5) about the marshlands and mosquito problem which led to a high incidence of malaria is relevant even though it is not a desirable quality. Just explain why the information expressed in each sentence is useful in the description of the topic. That should be what your teacher wants