第18题: [单项选择]I didn't go to his party last night, because ______ I changed my mind. A. on a second thought B. on second thought C. by second thought D. on the second thought 参考答案:B 答案解析:on second thought 是固定搭配,不要求用冠词,该题考查零冠词在固定搭配中的用法。相关区分词组还有take place 发生,take the place 代替;in place of