TOEFL Listening: ETS-TOEFL听力机经 - I3E8XP1N2F3H2ZC3P$

According to the professor, what is autoradiography able to reveal about a painting that regular X-rays cannot? A. The materials from which pigments were made B. The presence of darker shades under the surface C. How colors in the painting have changed over time D. The condition of the canvas