one term on left, 0 and 1 on right
three terms on left 1 and 2 on right
5 terms on left, 2 and 3 on right
7 terms on left, 3 and 4 on right
the relation between 0,1,2,3 and 1,3,5,7 is right=left*2+1
since the terms on left of question are 199 therefore
A looks 99
or simply just like 3 and 4 make 7 terms
99 and hundred make 199 terms