一道Prep SC比较结构的难题-求助

The environmental Protection Agency frequently puts mandatory controls on toxic substabces that present as little risk as one in a million chances to cause cancer.

(A) as little risk as one in a million chances to cause

(B) as little risk as one chance in a million of causing

(C) as little risk as one chance in a million that it will cause

(D) a risk as little as one chance in a million for causing

(E) a risk as little as one chance in a million for it to cause

给的答案是B.我想弄明白的是A为什么不对,还有以下问题:

1)A中的to cause和B中的of causing是修饰chances还是risk?  为什么?

2)百万分之一的机会是"one in a million chances"还是"one chance in a million"?

3)为什么是present as liilte as 而不是present a risk as lillte as

请帮助分析这道题. 

谢谢!

答案给的B.

谢谢Whitney.

其他几个问题能不能帮忙解释一下?

我开始也是看as little risk as，所以选错了，网上查了，也极少有as little risk as这种用法，不过今天又查了a risk as little as，也很少用，所以我想，GMAC这里考的是risk of causing，其他的不用管