In support of the facial feedback hypothesis, participants in one study reported

In support of the facial feedback hypothesis, participants in one study reported weaker emotional responses to positive and negative video clips than participants in a control condition.  What methodology was used to draw this conclusion?
 
A) Participants were injected with a placebo and told that it would enhance or inhibit their emotional experience.
B) Participants were injected with Botox or Restylane and then asked to view the video clips.
C) Participants completed a scale that asked them to report their level of empathy with others.
D) Participants were asked to try to imagine they were the characters in the video clips.
E) Participants were given mild electrical shock every time a computer registered a facial expression.