In a Study by Elizabeth Loftus, Subjects Watched a Film

In a study by Elizabeth Loftus, subjects watched a film of an automobile accident, then answered a series of questions, including one asking them to estimate the speed of the cars. What factor affected the subjects' estimate of how fast the cars in the film were traveling?

A) the presence of broken glass at the scene of the accident
B) the presence of a stop sign at the scene of the accident
C) whether the word contacted, hit, bumped, collided, or smashed was used in the question
D) the actual speed of the vehicle, regardless of the wording of the question