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