TOEFL Reading: ETS-TOEFL阅读机经 - 1735YYRL3JF6KGCEL$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Because cave art was not discovered until the 1860s and anthropologists and art historians did not begin studying it until 1902, we still have little knowledge of it. B. Cave art was first discovered in the 1860s, but it was not until 1902 that anthropologists and art historians first began to understand it. C. We know quite a bit about cave art, given that it was not discovered until the 1860s and not accepted as authentic until 1902. D. We know a reasonable amount about cave art as a result of the efforts of anthropologists and art historians since the first discoveries in the 1860s.