1.因为后面的做限定作用 前面的无需限定
前句中用“a” 后句的对“a”的限制才有意义
2.for可以引导原因2请具体分析一下句子，谢谢分析结构吗 可是没有for啊对不起，题错了，是for whichshe had an ambition to be an artist at an early age,(for wihch)she made every to become better and better。她在年轻的时候曾立志成为一名艺术家，她因此将一切做得越来越好，先行词是ambition。ambition放在从句中什么地方？for(the ambition) she made every to become better and better=（the amition) why she made every to become better and better