To a large extent, the activity of kidneys is controlled by .
a. your age
c. composition of your blood
b. your blood pressure
d. the food you eat

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?

If the dimensions of a cube-shaped cell with a length,height, and width of 1 micrometer were to double, what would be the cell's new ratio of surface area to volume? a.3 to 1 b.4 to 3 c.1 to 2 d1 to 6

Prokaryotic and eukaryotic cells are different in many ways other than the presence or absence of a nucleus. if both archaebacteria and eubacteria are prokaryotic cells, then why are archaebacteria more closely related to eukaryotic cells than they are to eubacteria?