Answer the following question given this paragraph: 

Chordates are defined by a set of four characteristics that are shared by these animals at some point during their development. In some chordates, all four traits are present in the adult animal and serve important functions. However, in many chordates, including humans, some traits are present only during the embryonic stage. After that, these traits may disappear.


Q: Chordates are defined by a set of four characteristics that are shared by these animals at some point during their?


A:
development