They have reversed the decision of retiring data recovery--
https://developer.salesforce.com/blogs/2021/03/salesforce-data-recovery-services-back-by-popular-demand

Anser is A Not C.

Earlier before around July 2020, Salesforce support was offering a feature to recover the data however, Salesforce has retired this feature due to integrity issues.

If you want to read more about it please visit the below article

https://help.salesforce.com/articleView?language=en_US&type=1&mode=1&id=000352139
And that is why frequent backups are extremely crucial however, in this scenario the last backup was done 3 months ago.
With that, we are left with only a single alternate and that is "Manually update the corrupt data to correct it."

Indeed it's a chaotic and lengthy alternate however, there is no other valid/suitable alternate from given choices.

The below options are incorrect:

"Log a Data Recovery case with Salesforce Support" is incorrect as per the above alternate.

"Use Data Loader to delete the corrupt data" is incorrect because deleting data would result in more chaos and entirely loss of data.

"Restore the data using the available backup" is incorrect because available data is 90 days older so it might not be very helpful and restoring that older data means giving away all the new updates on all of those records.......