Read the following passage and mark the letter A, B, c, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Stories about how people somehow know when they are being watched have been going around for years. However, few attempts have been made to investigate the phenomenon scientifically. Now, with the completion of the largest ever study of the so- called staring effect, there is impressive evidence that this is a recognizable and genuine sixth sense. The study involved hundreds of children. For the experiments, they sat with their eyes (21)                       so they could not see, and with their backs to other children, who were told to either stare at them or look away. Time and time again the results showed that the children who could not see were able to tell when they were being stared at. In a total of more than 18, 000 trials (22) _____ worldwide, the children correctly sensed when they were being watched almost 70% of the time. The experiment was repeated with the added precaution of putting the children who were being watched outside the room, (23)              from the starters by the windows. This was done just in case there was some pretending going on with the children telling each other whether they were looking or not. This prevented the possibility of sounds being transmitted between the children. The results, (24)                     less impressive, were more or less the same. Dr. Sheldrake, the biologist (25)                       designed the study, believes that the results are convincing enough to find out through further experiments precisely how the staring effect might actually came about.

For the experiments, they sat with their eyes (21)             so they could not see, and with their backs to other children, who were told to either stare at them or look away.