Londra and Sondra Are Identical Twins Who Have Been Raised

Londra and Sondra are identical twins who have been raised together in the same home.Londra has developed a psychological disorder,but Sondra does not appear to have the same disorder.What does this suggest about the disorder if this pattern holds for other identical twins

A)  Genetic factors have more influence than environmental factors in this disorder. 
B)  Both genetic and environmental factors contribute equally to this disorder. 
C)  Neither genetic nor environmental factors contribute to this disorder. 
D)  Environmental factors have more influence than genetic factors in this disorder.