Read this: Despite changing family roles during adolescence, the home environment and parents are still important for the behaviors and choices of adolescents. Adolescents who have a good relationship with their parents are less likely to engage in various risk behaviors, such as smoking, drinking, fighting, and/or unprotected sexual intercourse. In addition, parents influence the education of adolescence. A study conducted by Adalbjarnardottir and Blondal (2009) showed that adolescents at the age of 14 who identify their parents as authoritative figures are more likely to complete secondary education by the age of 22—as support and encouragement from an authoritative parent motivates the adolescence to complete schooling to avoid disappointing that parent.

Which researchers conducted a 2009 study that concerned adolescents, their parents, and secondary education completion?
What is the answer? (If it cannot be answered, return "unanswerable")
Adalbjarnardottir and Blondal