Scientist: A controversy in paleontology centers on the question of whether prehistoric human ancestors began to develop sophisticated tools before or after they came to stand upright. I argue that they stood upright first, simply because advanced toolmaking requires free use of the hands, and standing upright makes this possible.

Question: Which one of the following statements, if true, most weakens the scientist's argument?
Options:
A. Many animals that do not stand upright have learned to make basic tools.
B. Advanced hunting weapons have been discovered among the artifacts belonging to prehistoric human ancestors who did not stand upright.
C. Many prehistoric human ancestors who stood upright had no sophisticated tools.
D. Those prehistoric human ancestors who first came to stand upright had no more dexterity with their hands than did those who did not stand upright.
E. Many of the earliest sophisticated tools did not require their users to be able to stand upright.
Answer: "B"