In an trial, 100 people received thirty non-injurious electric shocks.

In an trial, 100 people received thirty non-injurious electric shocks. Fifty of them received twenty strong shocks, but the other half received weak shocks, except for three random strong shocks. The volunteers were told in advance which group they were in. The researchers discovered that the volunteers who consistently received strong shocks showed much milder physical signs of anxiety than the other volunteers did.

Which of the following would, if true, most help to explain the results of the experiment?

A. Other studies have found that the inability to predict when an anticipated unpleasant experience will occur usually provokes anxiety.
B. Most people feel more anxiety when anticipating a strong electric shock than when anticipating a mild shock.
C. Many of the volunteers who consistently received strong shocks reported that the shocks made them feel quite anxious.
D. The volunteers who received mostly mild shocks showed stronger physical signs of anxiety after each strong shock than after each mild shock.
E. People who knowingly volunteer for an experiment in which they will receive electric shocks typically feel less anxiety about such shocks than most other people would.