Justine and Diego cannot understand why their young son and daughter are constantly bickering. They can fight over the smallest thing and can pick up on the slightest hint of perceived injustice or lack of fairness. What is at the foundation of the children's behavior?

Evolutionary forces

Explanation:

Evolutionary forces are the forces that process evolution in human's life.Natural selection is the force that tends to spread behavioral pattern in a person along with forces like genetic drift, mutation and gene flow.

According to the question, behavior of children is based upon evolutionary forces that is acting as foundation to the quarreling behavior pattern of them.Thus, children can argue over any small topic of unfair behavior towards them.

industry had made the u.s. the richest nation in the world at this time. the second industrial revolution caused growth in industry and transportation, which allowed increased trade between nations.

this doesn't support enough information to answer the question.