—Was his father very strict with him when he was at school？—Yes he had never praised him

问题补充：

—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：

A. after

B. unless

(答案→)C. until

D. when

解析：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.