请高手帮忙分析下，为何答案要选E?

duan2008

several studies have found that the coronary patients who exercise most actively have half have half or less than half the chance of dying of a heart attack as those who are sedentary

A.have half or less than half the chance of dying of a heart attack as those who are sedentary
B.have half the chance ,or less , of dying of a heart attack than those who are sedentary do
C.have half the chance that they will die of a heart attack ,or less , than those who are sedentary do
D.are at least fifty percent less likely to die of a heart attack as those who are sedentary
E.are at least fifty percent less likely than those who are sedentary  to die of a heart attack

我当时选的是C，答案说B、C中than之前无比较级出现（less than是与之相并列的部分）
我第一时间可能不会想到OR的前后属于并列，所以同级和比较级共用一个than就是错误的
但是还是请高手帮我作一个合理的句子成分和语法的分析！为谢！

duan2008

没人回复啊，上次也是看了个GMAT对于一个语法题的讲解很是透彻，彻底佩服，但是现在找不到那个人了

aeoluseros

插入语不是句子主要成分，是可以完全省略不看的（可以理解为级别不同），所以B,C里面把or less作为了插入语，使得他们无法与than搭配。
所以只有E用了less ... than...的结构。

duan2008

谢谢你的答复，但是我觉得不够全面，能从五个答案每个再作个分析吗，仅仅是因为OR less是作插入语而排除不够让人信服

xiaoder1230

ABC 用 half or less 直接排除 D 项没有than 这题是选E么 不太清楚啊

duan2008

标准答案是选E