Look at this picture of a trilobite. these animals were once present in the ocean but are now completely extinct. what is a likely cause of trilobite extinction? a. something changed that brought these creatures onto land in a slightly different form. b. something changed to limit and finally abolish their success in this environment. c. they failed to develop vestigial organs that would have them survive. d. they were no longer able to acquire the necessary characteristics for survival in a changing environment.