He had never praised him ____he became one of the TOP students in his grade.
A, unless
B, until
答案选择B。
有人说可以改为：He had never praised him unless he was one of the TOP studetns in his grade.
请问这是正确的吗？
unless是表示将来的一种假设，后面应该不可以＋过去式吧。期望老师们能帮忙解答一下~
原题需要时间状语，不是条件状语。作题时是不可以改动原题的。
unless引导条件状语从句，即主句的动作发生与否是打造在条件是不是成立上，故主句的动作不可能在从句动作之前。而主句为过去完成时，unless从句为一般过去时，这种时间关系就是不对的。