The correct answers are A) four-field crop rotation and E) selective livestock breeding.
The adoption of the four-field crop rotation and selective livestock breeding helped to increase the amount of food produced per unit area of farmland.
Crop rotation was a great idea to better use the portions of lands destined to farming. People divide the same area to grow different types of crops in different seasons. If farmers grow the same crop for many years in a row it can cause the soil depletes nutrients. Rotating crops helps the soil to reduce erosion and increase fertility. Livestock breeding is the process where farmers breed animals such as cows, pig, chickens, and constantly reproduce them to have better production and trade their products.