option D
we need to find sum of series up to 'n' terms..
for n=1 sum =10
for n=2 sum =10+84=94
for n=3 sum =10+84+734= 828
now put value of n in each formula find compare. like for n=2
option A:- 9(92 +1)/10 +1 = 74.8 (rejected)
option B:- 9(92 -1)/8 +1 = 90+1=91 (rejected)
option C :- 9(92 -1)/8 +n = 90+2=92 (rejected)
option D :- 9(9 2 - 1)/8 +n2 = 90+4= 94 (Accepted Answer)