题目内容：
--Was his father very strict with him when he was at school?--Yes. He had never praised him _________ he became one of the top students in his grade.
参考答案：
答案解析：
单选题：--Was his father very strict with him when he was at school?
- 题目分类：中学英语
- 题目类型：单选题
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--Yes. He had never praised him _________ he became one of the top students in his grade.