One cell. Unicellular organisms are made up of only one cell that carries out all of the functions needed by the organism, while multicellular organisms use many different cells to function.
SI is a base 10 standardized system. I hope this helped and if not I highly recremend talking to your teacher or a parent.
Aerobic respiration is more efficient than fermentation because aerobic<span> respiration use oxygen molecule to break down.</span>