How many different types of cells can a blood stem cell make? A) 100 B) 8 C) 80 D)10

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?

1. fold your hands together so your thumbs cross over ,and look at your thumbs. which thumb feels most "comfortable" on top is actually controlled by a gene. the left thumb folding over the right thumb is a domi

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled