Why was the Roman Empire divided in half during the 3rd century A. D.?

Rick is a toddler with an easy temperament and active nature. people are often seen stopping to talk to him in supermarkets and parks where his mother takes him in the evenings because he smiles willingly at other children and adults. this aspect of rick’s behavior most likely reflects a(n) active genotype–environment interaction suppressive genotype-environment interaction passive genotype–environment interaction evocative genotype–environment interaction