Because it allows them to breathe and function.
The reason why nost scientists thought that the first true cells formed on Earth were anaerobic is being shown in the second option :B. because there was no oxygen on early Earth. Paying attention to this fact scientists discovered that first cells were prokaryotes and greatest part of them created oxygen as a toxic by-product of their own metabolism which make them understand how the planet was provided with oxygen and made a conclusion that first cells were anaerobic.
The answer is A, storing urine until it is eliminated.
The bladder stores urine, allowing urination to be infrequent and controlled. The bladder is lined by layers of muscle tissue that stretch to hold urine. The normal capacity of the bladder is 400-600 mL. During urination, the bladder muscles squeeze, and two sphincters (valves) open to allow urine to flow out.
She would find oxygen (O2) in the test tube because plants give off oxygen
