GMAT Sentence Correction (SC) | With adjustments for inflation,the relative cost of welfare

Any of the Moderators please reply.
Why D over C ?

As per me ,and is used
1. in case there are more than 2 elements in the list
2. to connect two independent clauses i.e. it begins a new clause with S-V pair.

But here we need to show the result of a previous clause, So i guess "-ing" Usage is better .

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