问题
选择题
—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.
A．after
B．unless
C．until
D．when
答案
C
never 与until形成搭配。句意：他成为年级中最好的学生时，他父亲表扬了他。从He had never praised him 可以看出父亲表扬过他是事实，所以B项unless（强调条件关系）不合题意。这样说是合情合理的：Yes, he would never praise him unless he could become one of the top students in his grade.