GMAT Sentence Correction (SC) | Re: In an effort to reduce the number of fires started by

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.
A. in which thin layers of extra paper are used to decrease the amount of oxygen entering the cigarette, thereby slowing
B. in whichthey use thin layers of extra paper in decreasing the amount of oxygen
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