If two mice both have grey fur, similar body shapes, and live in the same area,
they would likely have been considered the same species by linnaeus when he first developed his system of classification in the early 1700s.
what could be done today, that linnaeus could not do, to us determine more clearly if they are the same species?

a. we could compare gene or protein sequences between the two mice.
b. we could determine if it is possible for the two mice to be interbred.
c. we could take blood samples to see if the two mice have the same blood type.
d. we could track the mice with satellites to determine if they have the same habits.