Transitions connect thoughts from paragraph to paragraph.
In my opinion, the correct answer is A. unhealthy family relations. Even though the Usher siblings might be mentally ill, we don't see that from this excerpt, just like there are no hints at supernatural beings or weak women characters. We just see the eerie bonds that have connected all members of the family, along with the house as a "creature" of its own.
One example of irony is the fact that a rose, marked with both thorn and the color red.
