第27题: [单项选择]Consumers usually don't know ____________. A. where to buy cheaper things B. what materials are needed to improve finished products C. why they purchase some expensive products D. the brand names of products they buy regularly 参考答案:B 答案解析:[解析]事实细节题。文章第二段第二句指山“Yet too often consumers have no idea of...in selecting one product over another