Do Scientists Know What Causes Conjoining in Embryos

Do scientists know what causes conjoining in embryos.

A) Yes, they can induce it in other organisms, so it must work in humans in the same way.
B) Yes, the embryos twin and then get stuck back together somehow.
C) Yes, the embryos do not completely separate when they twin relatively late in development.
D) No. They can't induce it in other organisms, so they really have no idea what causes it.
E) No. What causes it is not clear.