All of the Following Scenarios Have Been Implemented as True

All of the following scenarios have been implemented as true experiments. Which one is LEAST likely to present the risks of demand characteristics?

A) Testing the effects of team-teaching versus a usual single-instructor teaching approach on students' test scores.
B) Testing the effects of a court-mandated substance abuse treatment versus probation on repeat offending.
C) Testing the effects of playing violent versus non-violent video games on geometry test scores.
D) Testing the effects of a video on drinking-and-driving dangers on the attitudes about driving under the influence.