Researchers Have Difficulty Determining Genetic Influences on Personality When They

Researchers have difficulty determining genetic influences on personality when they simply compare children with their parents. This is because

A) it is difficult to find comparable measures for children and adults.
B) genetic and environmental influences on personality are confounded when using this method.
C) it is difficult to find control groups that match the experimental groups.
D) we need to follow the development of the children's personalities for many years to determine genetic influences.