Answer:
las
Explanation:
Remember that to answer a question in spanish you have to read the context, in the question the person is asking who applies the injections in the clinic?
So we are talking about the injections, remember that in spanish there are different pronouns depending on if its singular, plural and femenine or masculine, injections in spanish is femenine, so it would be La or las, since its plural we use "las".
