A Researcher Studies the Rate of a Rare Blood Disease

A researcher studies the rate of a rare blood disease among monozygotic and dizygotic twins. She finds a much higher rate of concordance in the monozygotic twins. What might she conclude?

A) Both parents must be carriers of the disease.
B) Genetic factors play a strong role in this disorder.
C) The disorder is due to a chromosomal abnormality.
D) There are few, if any, environmental influences on this disorder.