明天要考了，请教一道题，拜谢！

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.

1. in which thin layers of extra paper are used to decrease the amount of oxygen entering the cigarette, thereby slowing

2. in which they use thin layers of extra paper in decreasing the amount of oxygen entering the cigarette, which slows

3. that uses thin layers of extra paper to decrease the amount of oxygen when it enters the cigarette, thereby slowing

4. for which thin layers of extra paper are used to decrease the amount of oxygen that enters the cigarette, and thereby slowing
5. using thin layers of extra paper in decreasing the amount of oxygen entering the cigarette, which slows

选A,我选的是C,为什么要用in which啊，a cigarette use thin layers of extra paper 很通畅阿

谢谢指点！

自顶下~  语法好像总是回的人很少嘛

c中it 没有明确指代，company，paper，oxygen都有可能

　that后面应该是完整的主渭结构，Ｃ中that后缺主语

这里ＷＨＩＣＨ清楚的指代cigarette

从后面entering the cigarette，可以看出extra paper 一定在cigaret

　　拙见，继续讨论

cigarette that uses  逻辑上不对

应该是被动关系

C项并不缺主语，that可以作为从句的成分，但是正如4楼说的cigarette that uses  逻辑上不对。

3楼的对于“从后面entering the cigarette，可以看出extra paper 一定在cigaret”的分析实在精辟，明显看出了出题人的提示。

群众的智慧真是无穷啊。