单词学习：once in a while 短语/副词短语
once in a while
/ˌwʌns ɪn ə ˈwaɪl/
偶尔；有时
Once in a while, Mr. Gu treats his students to ice cream after class.
偶尔，顾老师会在课后请学生们吃冰淇淋。
单词卡片
卡片已就绪
