What is the best description of organisms in the precambrian era? a. land plants and animalsb. dinosaurs and primitive mammalsc. single-celled organisms and soft, boneless animals. d. ferns and flying reptiles

How does human environment effect the biosphere

When is your breathing likely to speed up? a. when your white blood cells increase b. when your cells need more energy c. when your heart cells need more carbon dioxide d. when your blood cells have too much oxygen

Why do you suppose the structural polysaccharide cellulose does not contain branches?