you will see this product------whenever you go in this city.

C 这里是过去分词, 表示被动, 因为产品是被广告的.这里用过去分词作定语
就像是 I met a boy called Jim. called 表被动“叫做”
如果加be, 就成了谓语动词, 就是定语从句了.此句定语从句不能省略关代词.
必须是 you will see this product_that_is_advertised___whenever you go in this city. 这句和你的句子是同义句, 只不过用的定语从句.
希望能帮助到你.