How is a subspecies different from a species?

The meseta in spain is a a. navigable river b. castle c. coastal plain d.plateau

Which revelation resulted from the observation of the spectrum of different galaxies? a. there were more galaxies whose spectrum was blueshifted b. there were no galaxies whose spectrum was redshifted c. there were more galaxies whose spectrum was redshifted d. there were no galaxies whose spectrum was blueshifted

During which era in earth's history were the first insects? mesozoic precambrian cenozoic paleozoic