In the Study of Behavior Genetics, in Which of These

In the study of behavior genetics, in which of these situations would Jack and Jill be half siblings?

A) Jack and Jill are siblings born of the same parents but now Jill lives with her mother and her new husband and his two children while Jack lives in his own apartment
B) Jack's mother married Jill's father, creating a new household up the hill where they all lived together happily ever after
C) Jill's mother, the former, Mrs. Hubbard, marries Mr. Spratt and two years later they have a child together and name him "Jack"
D) a & b
E) b & c