Answer:
My favorite horror movie is Rosemary's Baby. The reason is because I feel it is very refined in the way that it is scary. It doesn't need much gore or jump scares to be thrilling like the movies of today. The plot structure and the way it flows are also impressive given the complexity of this movie's plot. Lastly, I love that it's based on a book because it gives even more opportunity to compare the two.
Explanation:
I know it sounds super fluffed up and stuff but you said you needed it for school so I tried to make it as professional sounding as I could :)