The correct option is A Sunday
Given, Nisha was born on 30 January and during that year, Republic day (or 26th January) was celebrated on a Wednesday.
So, Nisha was born on 30th January i.e., Sunday.
Now, Reshma is older than Nisha by 21 days. So, Reshma must be born on 9th January (= 30 - 21).
Hence, 9th January will also be a Sunday.