This is the cookie-cutter flaw of circular reasoning, where the argument’s conclusion simply restates one of its premises. The author doesn’t make this mistake; her premises may not support her conclusion well, but they are distinct from her conclusion.

The author does conclude that rational-choice theory is false, but not on the grounds that the evidence for it is hypothetical. Instead, she concludes it’s false based on examples that she believes prove it to be false.

Actually, the author assumes that people who are acting in ways that are not personally beneficial did not expect that their actions would be personally beneficial. (C) has this backwards.

The author never assumes there are more examples of people acting in ways that are not personally beneficial than people acting in ways that are. She just says there are “plenty” of examples of people acting in ways that don’t benefit them, which she thinks disproves the theory.

Just because people sometimes act in ways that don’t benefit them doesn’t mean that those people weren’t expecting to benefit from their actions. If they were, the author can’t conclude that rational-choice theory is incorrect.