The idea for Buy Nothing Day first started in ______ .

C
事实细节题。题目询问“举办‘不购物日’的提议最先是在哪里开始的?”从文章第二段第二句话The idea for Buy Nothing Day started in Vancouver，British Columbia可知，最先开始“不购物日”的是英国哥伦比亚省的温哥华市。正确答案为C。