In 2015, by what percent should the votes of C increase to exceed the votes of B in the same year by 12% ?

B's votes in 2015 were 3.9
We want C's votes to be 12% more, which would be (1.12)(3.0 = 4.368 lakh votes. 

C originally got 2.3 lakh votes in 2015
C would require 4.368-2.3 = 2.068 lakh votes

This is close to the real value itself, so we can guess that the answer would be close to 100 percent. 
Upon calculation, we would get: $$\frac{2.068}{2.3}\times\ 100=89.91\%$$

Therefore, Option C is the correct answer.