Process by which old red blood cells are normally removed

Which group is noted for the independence of gametophyte and sporophyte generations from each other? a) ferns b) mosses, hornworts, and liverworts c) charophytes d) angiosperms e) gymnosperms

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?

Why has two different alleles for the same trait?