My teacher told us he’s a virgin while he was looking at me.. creepy

What are two reasons for why a species might disappear from the fossil record?

The circles, or orbits, for electrons are called energy levels. each level can hold only a certain number of electrons. add electrons to each level until you can't add any more. how many electrons can each level hold?

Compare and contrast region e in the illustration above with region d. describe the physical characteristics of each region.