TOEFL Reading: ETS-TOEFL阅读机经 - XL3X2N7U6616V7CWL$

Paragraph 6 suggests that the first eyes probably A. came into existence long before 600 million years ago B. came into existence at a late point in the Cambrian period C. existed before the animals of the Burgess Shale existed D. were larger than those of animals found in the Burgess Shale