A Strong Piece of Evidence That Genes Alone Do Not

A strong piece of evidence that genes alone do not cause the vast majority of mental disorders is that genetic studies

A) rely too much on twin studies and not enough on adoption studies.
B) rely too much on adoption studies and not enough on twin studies.
C) typically find concordance rates for DZ twins far below 100 percent.
D) typically find concordance rates for MZ twins far below 100 percent.