Someone Claims That "If a Characteristic Is Highly Heritable, Then

Someone claims that "if a characteristic is highly heritable, then we cannot change that characteristic by changing the environment." An example that argues strongly against this claim is that

A) monozygotic twins resemble each other more than dizygotic twins do, for a wide variety of behaviors.
B) adopted children resemble their biological parents with regard to many physical and behavioral conditions.
C) a special diet can prevent the mental retardation associated with PKU.
D) people with two genes for Huntington's disease get the disease, but people with only one such gene do not.