书店对话场景词汇：
Bookstore：书店
full refund [ful] [ri?f?nd, ?ri:f?nd]n.退款
retreat[ri?tri:t]n.退书
merchandises[?m?:t??ndaiz]n.商品
purchased ['p?:t??st] =buy [bai] vt.买
policy [?p?l?si]n.规定
store credit [st?:] [?kredit] n.商店退款;赊账购物
