GWD里一道语法题 求解

DebugXY222

In an effort to reduce the number of fires started by cigarettes, a major tobacco company is test-marketing a cigarette in which thin layers of extra paper are used to decrease the amount of oxygen entering the cigarette, thereby slowing the rate at which it burns and lowering the heat it generates.

in which thin layers of extra paper are used to decrease the amount of oxygen entering the cigarette, thereby slowing
in which they use thin layers of extra paper in decreasing the amount of oxygen entering the cigarette, which slows
that uses thin layers of extra paper to decrease the amount of oxygen when it enters the cigarette, thereby slowing
for which thin layers of extra paper are used to decrease the amount of oxygen that enters the cigarette, and thereby slowing
using thin layers of extra paper in decreasing the amount of oxygen entering the cigarette, which slows

为什么要用in which不能用that

很多资料说C错误是因为it的指代问题 但是感觉根据RON的说法 G里面有很多指代不清 感觉it指代并不能成为排除一个选项的原因

求解～

十分感谢～

vi.len

我觉得是因为AC之中，A更perfect。指代不清确实不是致命的错误，但是C中的it确实unclear。是extra paper进入还是oxgen进入？
最主要的是，A很完美，没有瑕疵。而C是有瑕疵的。
SC选的永远是最佳答案

Cynth1aC

http://forum.chasedream.com/foru ... amp;fromuid=1110890

#10的MM解答的已经很好了~