Nice example Uma.
I don't like the question. Plot is rather lousy and selecting 12 is questionable to me. Why not 14? I could probably even manage to draw a reasonable line that will give answer 15 (C).
Edit: this is not the only question I don't like. Question 4 - I have no idea which method will be the best, I would try both spectroscopy and conductometry, to check which gives better results. Question 6 - answer is almost three times larger than the Ba(OH)2 solubility at the room temperature. No idea if it gets better later.