This problem will be discussed next month, by____ the school leaders will have to make up their minds about what to do with the problem.
A.when B. which C.that D.whom
答案是A。解释是when作by的宾语，when是定从，修饰next month。我认为by应该是加关系代词的啊，有介词加关系副词指导定语从句的吗？我没见过。请英语高手帮忙解决

This problem will be discussed next month, by____ the school leaders will have to make up their minds about what to do with the problem.
A.when B. which C.that D.whom
答案是A。解释是when作by的宾语，when是定从，修饰next month。我认为by应该是加关系代词的啊，有介词加关系副词指导定语从句的吗？

回答：此题有一定难度。因为，by短语是指时间的起点，而不是那指一段时间，所以，这里的when便有from the beginning of next month,与which相比更具体，故此答案是正确的。