单选题 The chief function of unmailed advertising is ______.

A、 to send sample products from door to door
B、 to familiarize the customers with the products
C、 to deliver the products directly to the retail stores
D、 to send information about the products in quick ways

【正确答案】 B

【答案解析】由第四段used for the same broad purposes as direct-mall advertising可知unmailed advertising的主要作用与direct-mall advertising一样，都是使消费者熟悉该产品(to familiarize prospective buyers with a product)。