Background extinction is a measure of
◦ the rate of species turnover at the end of geological eras.
◦ the number of species that suffer extinction at the beginning of geological eras.
◦ the steady rate of species turnover within a lineage throughout most of their evolutionary history.
◦ the lowest rate of species turnover within a lineage observed within a geological era.
◦ the animals that appear in the dense forest.