The correct answers are A) four-field crop rotation and E) selective livestock breeding.
The adoption of the following two practices helped to increase the amount of food produced per unit area of farmland: four-field crop rotation and selective livestock breeding.
It was during the 16th century that new agricultural technologies innovated the way farm fields were worked. The four-field crop rotation that allowed farmers to diversify the kind of crops that grew in the same place, represented a great advancement for agriculture. Something similar happened with the breeding of selective stock in farms. New advancements in animal nutrition allowed the production of better food that could be traded at better prices.