Confusion

Marcia tries to make the point that not all vegetarian diets will lead to nutritional deficiencies, i.e. some vegetarian diets will not lead to nutritional deficiencies. She cites research as evidence for this claim. Theodora responds by stating that Marcia is wrong in claiming that vegetarianism cannot lead to nutritional deficiencies and continues to show why Marcia is wrong on this front. We can stop right here. What's the issue? Marcia did not make the claim that vegetarianism cannot lead to nutritional deficiencies. Marcia states that some vegetarian diets will not lead to nutritional deficiencies. These are two very different claims. This is exactly what answer choice (A) points out. Hope that clears things up! Please let us know if you have any other questions.

so is the biggest takeaway for this question the distinction between "not all" and "all"?