When monozygotic (MZ) twins who were discordant for schizophrenia were compared with MZ twins who both had schizophrenia, researchers found that the MZ twins discordant for schizophrenia:

A) possessed additional genetic material not found in members of the control group.
B) had the exact same DNA structure, thereby implicating environmental factors.
C) showed numerous differences in the molecular structure of their DNA.
D) had few, but noticeable, variations in their genetic makeup.