39. According to the passage, Cho would have determined
that volunteers had experienced a placebo effect if
which of the following procedures had created
increased activity in the visual cortex of the brain?

  • A. Flashing a light in front of them

  • B. Stimulating one of their vision-related acupoints

  • C. Having them read an eye-examination chart

  • D. Stimulating a place that was not a visual acupoint