All of the statements you provided address different aspects of the tensions between Iran and the Kurds. However, if you are looking for the one that most directly investigates the tension, it would be:
"The Kurds wish to have their own state since they have been forced to assimilate in Iran."
This statement highlights the desire for autonomy or independence among the Kurds and suggests that Iranian policies have contributed to their tensions, making it a focal point of the investigation into the relationship.