According to the current definition of a species, which of the following is an example of a species?
select one:
a. two rehesus monkeys with slightly different physical features mate to produce fertile offspring.
b. in a population of frogs, one type of frog mates in early april while the other mates in late june
c. a coyote and wolf housed together in a zoo pen
d. a donkey and a horse mate to produce a mule that is sterile and is unable to produce babies