Which generation in ferns is the dominent generation​

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

Can someone i have no idea of how to do this.