It should be D. A would make sense but there is not connection with the conversation which can sometimes be considered a unhealthy practice. Taking turns cooking doesn't involve talking, so it doesn't make sense (not b). While attending events that are important to others is a good thing, again it doesn't involve talking, so it's not C. That leads us to members relate to one another in different situations (d). That makes sense because in order to relate in different situations, it requires an unified, general topic that involves healthy communication.
