TOEFL Listening: ETS-TOEFL听力机经 - BJ45PZPX4NO559C1P$

What is the professor's main point about the markings on the cave walls? A. Their discovery led to a new theory about the origins of art. B. Their use led to a burst of creativity in early human history. C. The markings may be as important as the paintings they accompany. D. The markings have changed archaeologists' ideas about where human culture first developed.