Question

What best explains why towns and cities grew during the middle ages

Answer 1

There were rapid advances in agriculture, like the three-field system, and moldboard plow.

The "three field system" is basically where a farmer would plant some grain (wheat, barley, or rye) during the autumn, and then a spring planting of peas (or some type of bean) and more grains. Then, the field would be left fallow until the autumn, where the farmer would start over again. This system was much better for the soil than the previous, two field system (one harvest per year, then leaving the field fallow), yielding more food, and more importantly, more food security. This means that less people needed to farm, and a higher population could be sustained.