Sentence Correction

little mice wrote:In 1852 Robert Angus Smith published a detailed report of the chemistry of rain kin a large area around the city of Manchester, England, noting that the closer one came to town, the more the city air would become increasingly acidic.

Athat the closer one came to town, the more the city air would become increasingly acidic - tense problem
Bthat the city air became increasingly acidic the closer one came to town
Cthat coming closer to town, the city air became increasingly acidic - modifier problem
Dthat the more the city air became increasingly acidic, the closer one was to town
Ethe city air becoming increasingly acidic as one would come closer to town - missing that!

the OA is B
could you please explain why? (every choices~~) thanks in advance~