TOEFL Reading: ETS-TOEFL阅读机经 - 34VV0NQR9FY9A3ZFL$

According to paragraphs 3 and 4, what was remarkable about the Cambrian explosion A. That the evolution of species occurred so soon after the first eukaryotes appeared B. That most of the known animal types appeared in a relatively short period in history C. That many of the animal types that appeared in the period have survived until today D. That the pace of evolution slowed before it accelerated