In a Meditation Training Study Where Participants Learned to Meditate

In a meditation training study where participants learned to meditate over the course of eight weeks, researchers found that:

A) the new meditators showed gray-matter density increases in several cortical areas.
B) cortical thickness was negatively correlated with meditation experience.
C) meditation does not alter the brain.
D) the new meditators showed gray-matter density decreases in several cortical areas.