Passage Summary: Marcia says vegetarianism can be healthy; Theodora argues that if everyone did it, the economy would tank and people would be too poor to eat well.

Conclusion: Marcia is incorrect in her assertion that vegetarian diets do not necessarily result in nutritional deficiencies.

Reasoning: If a large-scale shift to vegetarianism occurred, the resulting economic collapse of meat industries would lead to poverty, preventing former workers from buying healthy food.

Analysis: Theodora is guilty of a classic 'straw man' or 'red herring' fallacy by shifting the goalposts of the argument. Marcia is making a point about the nutritional content of a specific diet, while Theodora responds by discussing the macroeconomic consequences of a societal shift. Look for an answer that points out how Theodora fails to address the actual nutritional potential of the diet itself, focusing instead on external economic factors. It's a bit like arguing that bicycles aren't a valid form of transport because if everyone stopped driving, car mechanics would go broke and couldn't afford bus fare.