This is a question in an old exam of Histology. I tried to answer the question, and I've made many searching attempts, but without resulting in any fixed/exact information. In some articles on the web, I've read the stereocilia and microvilli have both actin core, and this website states that stereocilia doesn't have actin filaments! I'm just feeling lost at this point. And now, I'm just searching for an exact answer for that question.
Note : It may be a super easy question for you. So please note that I'm a novice self-learner at Histology.