Which shape is most similar to that of DNA? A chicken egg
A line of spheres, each smaller than the one before it
A series of figure eights wound around each other
Two wires twisted together

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

What causes darkening of the skin as melanin production increases

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen