What Led to the Development of Family Systems Therapy

What led to the development of family systems therapy?

A) The observation that signs of mental illness often were seen in more than one family member
B) The recognition that most psychological disorders can be attributed to and cause dysfunctional relationships
C) The realization that the family environment played a role in whether relapse occurred
D) The established importance of the interaction of nature and nurture in the development if all forms of psychopathology