A is quota and C is stratified. Stratified sampling is a random sampling method, whereas quota does not have to be. Eg they could fill the quota using a non random method like convenience sampling within each branch. I hope that makes sense.
@CMOMaharashtra Sir, We can use these testing techniques before lifting lockdown from each district. As we don't know the exact spread/ impact of covid exactly.
(Stratified Random Sampling+Quota Sampling+Judgemental Sampling)