Adenosine triphosphate, or atp, is primarily used as in living organisms.

a.) a muscle relaxing hormone
b.) a source of energy
c.) a blood coagulant
d.) a reproductive enzyme

the supermassive black hole is in the middle of the galaxy.

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.