the doctor warned the patient ____ smoking A of B against C at D for

问题描述:

the doctor warned the patient ____ smoking A of B against C at D for

选B
解析:warn sb against/about sth劝告(使有所防备);警告;告诫
warn sb of sth提醒注意(可能发生的事);使警惕
原文意思是医生警告病人要远离烟所以选B好一些.