【正确答案】 C

【答案解析】[解析] 本题考查代词指代。由文章最后一句话“In other words，both buyer and seller should be fully aware of all the factors that comprise the total "package" being exchanged for the asked-for amount Of money in group that they may evaluate a given price”，可以看出“they”指的是句子的主语“buyer and seller”买者和卖者。因此选项[C]为正确答案。