For part A, we can control the bacteria and fungi by heating. For the result are different.
Part B, it is obvious that we can destroy fungi and bacteria by UV light, because the side of the plate that open to uv light do not have any microorganism remain, for both 15 minutes and 60 minutes.
Part C, the onion is the most effective antibiotic from Bacitracin, garlic, onion and Dettol.