单选题 John doesn't believe in ______ medicine; he has some remedies of his own.

【正确答案】 D
【答案解析】四个选项的意思为：standard标准的；regular通常的；routine日常的；conventional 常规的。故答案为D。[句意]约翰不相信常规的药品，他有着自己的治疗方法。