How are atoms held together in molecules? A. They combine to form polymers
B. They form covalent bonds
C. They break hydrogen bonds
D. they form ions

In many humans, exposing the skin to sunlight over prolonged periods of time results in the production of more pigment by the skin cells (tanning). this change in skin color provides evidence that -

What's the waste product of electrons and pyruvate combining in fermentation?  

What is responsible for the uneven heating between the poles and the equator on any given day