When sharing a post, or comment from lemmy, which link should you share?

Say you have a Community on Instance A, a User-B from Instance B posts to that community, a User-C on Instance C comments on that post, and User D on Instance D is viewing that post, and its comments from Instance D. How should user D go about sharing a comment from that post? Should User D share the comment from Instance D, Instance A, or Instance C?