Arecent newspaper headline reads "teenagers use more drugs if their friends use drugs." it implies that hanging out with drug-abusing friends can cause subsequent drug use disorder. the major problem with this assumption is that it assumes the direction of alternately, perhaps teenagers who are using drugs may select friends who also use drugs.

I believe the answer is: causality.

The initial assumption above  is that a teenager who use drugs would most likely influence other non-users to use drug. There is nothing from the finding that disprove otherwise. So, when user hang out with non-users, there is a pretty good chance that the non-users could influence the users to stop consuming the drug.

c is the answer for this