TOEFL Reading: ETS-TOEFL阅读机经 - TS780344HA5NKLT8L$

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. The simplest explanation for the similarities between birds and crocodiles is that they evolved at the same time. B. A common ancestor is probably the source of the shared traits of crocodiles and birds. C. The originally similar traits of birds and crocodiles increased after evolving through a shared ancestor. D. Only one shared pattern of behavior – that of nest building – was present in the common ancestor of birds and crocodiles.