What Is the Main Difficulty with Drawing Conclusions About the Relationship

What is the main difficulty with drawing conclusions about the relationship of genetics and criminality on the basis of twin studies?

A) Most twin studies were conducted in Scandinavian countries.
B) Dizygotic and monozygotic twins cannot be reliably distinguished.
C) The base rate of criminal behaviour is too low to reliably measure.
D) Monozygotic twins may be treated more similarly than dizygotic twins.
E) Most of the study results were politically driven.