Answer:
Answered
Step-by-step explanation:
Though many are apt to believe that the bones from a recent discovery are those of a direct ancestor of modern humans, some scientists are skeptical, and contend that the remains, while suggesting a common ancestor, are but a vestige of one of evolution's many_ unsuccessful._____ experiments.
On looking at the keyword vestige which means remains. If something is in remains of something and it is evolution, then that thing must have been unsuccessful. Rest all options look absurd with context of the question.