TOEFL Reading: ETS-TOEFL阅读机经 - 6YV2MJ59T9_4945RL$

According to paragraph 5, which of the following is true about the Olmec symbolic code A. It included only animals that have paws or wings. B. It did not change significantly from one century to the next. C. It was not strongly connected to Olmec religion. D. It developed gradually over a thousand-year period.