Which of these are paralogous genes?
a. the result of a gene duplication within a species; for example, a copy of the original hemoglobin gene has become adapted for slightly different functions within a mammal species as hemoglobin α and β
b. the result of a speciation event; each derived species has evolved a different version of the gene, like the difference between hemoglobin α in humans and chimps
c. genes located on the same chromosome and that are genetically linked, like freckles and hair color in humans
d. genes that have independently evolved the same function in distantly related organisms, like the hearing gene, prestin, which allows echolocation in both dolphins and bats
e. genes that have changed within a species as a result of adaptive evolution, such as improvements in the defensins proteins of the human immune system over time