against doing sth 如：warn sb against do sth 告诫某人别做什么 He often warns me against smoking.=He often warns me not to smoke.他经常告诫我别抽烟 【希望帮助到你，若有疑问，可以追问~~~祝你学习进步，更上一层楼！(*^__^*)】
against 是介词
