What does a virus need to bind to before it can enter host cells

Ageologist determines that a sample of a mineral cant be scratched by a steel nail but can be scratched by a masonry drill bit based on this information the sample mineral has to be softer than

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 first generation of offspring from the cross of two parents is called the a.f1 generation b.f2 generation c.short generation d.p generation