This is one of the exceptional question.

OA is C

reasoning: we need contrast here so BUT is needed.

Eg: Pinto is earning millions of bucks BUT his expenses are also soaring.


From 1965 on, region's standard of living has soared, BUT SO HAVE unemployment and prices


a) is wrong because we need a verb after BUT - since but is used to join 2 independent clause (that contains a subject and a verb)


e) is wrong because it says "SO DID" but how can "unemployment and prices" do something.


Hope it helps.