单选题 To my surprise, the strict teacher smiled at me ______ when I answered his question.
【正确答案】 D
【答案解析】根据句子结构,空格中要填状语修饰smiled,故A项friendly是形容词,以-ly结尾的形容词,故排除C项;in a+adj+way/manner为一固定表达。