What is the columbian exchange?

The travel between the Old and the New World was a huge environmental turning point, called the Columbian Exchange. It was important because it resulted in the mixing of people, deadly diseases that devastated the Native American population, crops, animals, goods, and trade flows.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.