From the problem data:
Total number of persons who read both newspapers in Dighospur = $200$.
In Dighospur, persons who read Ganashakti = $121$ (given in problem statement).
In Dighospur, persons who read Anand Bazar Patrika = $117$.
To find the number who read only Ganashakti, we subtract the people who read both from the total Ganashakti readers.
Only Ganashakti readers = Total Ganashakti readers $-$ Both readers.
= $121 - (200 - 117)$.
First, find “both readers” in Dighospur: Since Anand Bazar Patrika readers are $117$ and total readers of both newspapers in Dighospur are $200$, the overlap = $121 + 117 - 200 = 38$.
Thus, only Ganashakti readers in Dighospur = $121 - 38 = 83$.
Wait — rechecking: the question says "total number of persons who read these two newspapers in Dighospur is 200", which is union, not intersection.
Union formula: $G + A - \text{both} = 200$.
Substitute $G = 121$, $A = 117$: $121 + 117 - \text{both} = 200$.
$238 - \text{both} = 200 \Rightarrow \text{both} = 38$.
Only Ganashakti readers = $121 - 38 = 83$.
Hence, the correct answer is $83$.