In my youth / I used to / visit / Sharma's and Chawla's company.

The answer is Option D: Sharma's and Chawla's company.
Here's why:
When two people own a business together, and you want to show possession with an apostrophe,
you only need to add the apostrophe and 's' ('s) to the last name.
This indicates that they are jointly owning the company.
So, the correct way to write it would be "Sharma and Chawla's company".
If it was "Sharma's and Chawla's companies", it would mean they each own separate companies.
The other options are grammatically correct in this sentence.