Each statement in a dichotmous key has only 2 choices and they should be

How does a gymnosperm prevent itself from pollinating the same tree

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.

The negative impacts of nonnative species generally outweigh the positive impacts