Passage A points out that for an eco-bag to be truly effective, it must be 'used repeatedly.' Passage B provides a real-life example of a person who buys eco-bags but doesn't use them, thus just 'accumulating more things,' which is counterproductive. Both texts suggest that simply buying an eco-friendly product is not enough; how it is used is crucial. Therefore, the correct answer is 'The effectiveness of environmentally friendly products changes greatly depending on how they are used.'