PREP 159以及限定性从句的问题

cvtty

The first detailed study of magpie attacks in Australia indicates that (by the time they had reached adulthood, 98 percent of men and 75 percent of women born in the country have been attacked by the birds)
A. by the time they had reached adulthood, 98 percent of men and 75 percent of women born in the country have been attacked by the birds
B. by the time they reach adulthood, 98 percent of men and 75 percent of women, who were born in the country, had been attacked by the birds
C. by the time they reached adulthood, 98 percent of men and 75 percent of women born in the country had been attacked by the birds
D. 98 percent of men and 75 percent of women that were born in the country were attacked by the birds by the time they reach adulthood
E. 98 percent of men and 75 percent of women who were born in the country, by the time they reached adulthood had been attacked by the birds

请问，这句B和C的修饰有什么不同吗？
限定性从句和非限定性从句应该如何区分？用法有什么不同呢？
谢谢

michaelmay17

个人区分非限定性与限定性是用先行词后的“，”来区分的。
然后用法上的区别我觉得还是og10里的解释比较好，如果这个定语从句对句子理解至关重要，去掉的话会不好，则用限定性定语从句，相反，可有可无的成分用就使用非限定性从句。

HarrisZheng

which 和that 做定语从句引导词时候的区别：
其实他们的区别不是简单有没有逗号的区别

在某些情况下, 限制和非限制定语从句是有很显著区别的    that 只强调所修饰的部分, 而which修饰整体

比如 50% of the dogs that are male have been adopted.  表示有一群狗, 其中50%的小公狗被领养了  
又比如 50% of the dogs, which are male, have been adopted 表示有一群狗中, 50%为公狗, 他们被领养了
用数字来形象描述一下的话 假设有一群狗 一共100只，雌雄各50只，第一句说明有25只公狗被领养，而第二句说明有50只狗被领养，这些被领养的狗都是公的。这意思显然是不一样的。

这才是真正的限制性和非限制性的区别 也是他们为什么叫限制性定语和非限制性定语的缘由

记得OG中也有一道关于化学污染物的题 就是定语从句的区别 一下子找不到了

HarrisZheng

在本题中 B和C表达的意思是不同的

B表示的是 在这个国家出生的总人口中的98 percent of men and 75 percent of women  
C表示的是 98 percent of men and 75 percent of women，这些人出生在这个国家

michaelmay17

这是08prep'语法笔记的解释
    限定性与非限定性实质是：有该修饰时，修饰对象的外延是否有变化，如果变小了就是限定性，如果没变就是非限定性。
    形式上简单的看，有没有逗号是明显标志。有逗号就是非限定性，没有逗号就是限定性。
    实际上现在分词作定语如果没有逗号也是限定性，只是因为在GMAT中现在分词本身具有“客观状态”和“正在进行”意味，没有多种时态问题（这也正是现在分词完成式不做定语的原因），才使得其具有表达“重复多次性"意味的功能；而定语从句能够表达多种时态，因而倾向于表达”具体一次性“意味。