Answer:
A - Refrigeration & trash collection
Step-by-step explanation:
100 years ago, rotting meat & other fermenting food items were a huge problem, especially in close quarters. Refrigeration now keeps foods at a stable temperature, preventing bacteria growth, and trash collection removes possibly infected & contaminated items. For a basic view, nobody in modern society would willingly eat warm, raw meat, and most people have never considered eating out of the trash. Moldy food is quickly disposed of.