一道有关定语从句的高中英语题

一道有关定语从句的高中英语题
The Greens will move into the new house next Monday,( )it will be completely finished.
A.by the time B.by which time C.by that time D.by this time
括号中应选择哪个选项?为什么?这道题在考察什么?

The Greens will move into the new house next Monday,( B )it will be completely finished.
A.by the time B.by which time C.by that time D.by this time
考点：介词+关系代词引导的定语从句
翻译：格林一家下周一就会搬到新房子里,到那时房子就全建好了.
答案解析：定语从句 by which time it will be completely finished 修饰 next Monday,该从句的完整句是：it will be completely finished by next Monday.变从句是,将next Monday提前成为先行词,并用关系代词which time (when也可以) 代替原句成分,将介词+关系代词（by which time) 作为引导.