WBJEE 2016 Math Solved Paper

There seems to be a printing mistake here
If there are (2n–1) terms instead of (2n + 1) terms then nth terms of the A.P., G.P. and H.P. are the A.M., G.M. & H.Mof the first and the last terms.
So, a ≥ b ≥ c & ac - b2 (B, D)