Answer:(B)that the city air became increasingly acidic the closer one came to town
Explanation
(A)The comparatives used in A are 'the closer ... the more. The correct way of writing this would be the more one came ... the more the city air became...'
Another mistake in A is redundancy - 'more' and 'increasingly'.
(B)that the city air became increasingly acidic the closer one came to town
No redundancy. Conveys the meaning well.
(C)that coming closer to town, the city air became increasingly acidic.(example of dangling modifier)
(D)that the more the city air became increasingly acidic, the closer one was to town.(It is the example of inverse cause-effect.)
(E)the city air becoming increasingly acidic as one would come closer to town( use of would come is wrong here)