The author does project many individuals' responses collected at one time, by using the survey data to construct a hypothetical example. And the hypothetical example is of a single individual, whose responses the author imagines at different ages in the past. This technique is used in the argument.

You might notice that this isn't a complete description of the argument, because it doesn't include the author's appeal to common sense. But that's okay! All of (A) is accurate even though there's still more to the argument, so (A) is still correct.

The author arguably reinterprets what people actually said, by constructing those responses into a representative hypothetical example. However, the author never considers what would have been the most reasonable thing to say, so that's where (B) fails. The author never questions the reasonableness of individual responses.

No part of (C) accurately describes the argument. There is no excessive generalization in the argument: the result of the survey isn't applied to anything beyond its scope. And the author doesn't use any counterexamples, only a hypothetical example that aligns with the survey results rather than countering them.

The author does rely on a contradiction, but the contradiction is between a logical implication of the survey results and common sense, not between any two specific statements. Perhaps more importantly, the author doesn't try to disprove anything. The point isn't that the survey results are wrong, nor that common sense is mistake, but just that there's an issue with interpreting the results.

While the survey responses are pretty unanimous, the author never states that this unanimity is unexpected. And more strikingly, the author never raises a question of manipulation—the survey results are treated as a legitimate finding, the issue is just with interpreting them.