一道高中英语语法单选,谢

_____ would have taken our ancestors days to reach,是定语从句,修饰先行词places。但是,并非所有以place作为先行词的定语从句都在用where作为引导词。从句的引导词先用关系代词还是关系副词,取决于关系词（即先行词那个词的意思）在从句中（注意是从句中）充当主、表、宾、定；还是充当状语。如下面两句：we talked about the place which we would reach soon。we talked about the place where we would find some food。一句中,定语从句which we would reach soon(在句意上完全等于we would reach the place soon),其中关系词用了which,是因为which（所指的即是the place）在从句中充当reach这个动词的宾语,故用which这个关系代词。二句中,定语从句where we would find some food(在句意上完全等于we would find some food at the place),其中关系词用了where,是因为where (相当于“介词+which”,即相当于 at the place),在从句当中充地点状诘,故用where这个关系副词。所以所提问题的句中,从句从句意角度,缺少 would have taken our ancestors days 这个谓语结构的主语,名词才能充当主语,地点状语不能作主语的,所以用关系代词which,而不能用作地点状语的where。主语的意思是：我们一小时后能到达那里。从句的意思是：我们的祖先也许会花费数天才能到达那里。主从句合起来（强调定语的译法）：我们一小时后能到达我们的祖先许会花费数天才能到达的地方。从句中的take,表示“花费”之意,用would have take表示“本会。而实际上没。”（所以句中翻译作也许）,to reach作目地状语,表意“为了到达”。