Kelly and Shelly Are Identical Twins Who Have Been Raised

Multiple Choice

Kelly and Shelly are identical twins who have been raised apart, in separate adoptive homes. Shelly has developed a psychological disorder, but Kelly does not appear to have the same disorder. This information could be used as evidence to suggest that

A) genetic factors have more influence than environmental factors in this disorder.
B) environmental factors have more influence than genetic factors in this disorder.
C) both genetic and environmental factors contribute equally to this disorder.
D) neither genetic nor environmental factors contribute to this disorder.