I believe that the best answer among the choices provided by the question is are the following :
<span> H2O2
H2O
</span><span>catalase</span>
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ALVEOLI are the very small air sacs where the exchange of oxygen and carbon dioxide takes place. CAPILLARIES are blood vessels in the walls of the alveoli. Blood passes through the capillaries, entering through your PULMONARY ARTERY and leaving via your PULMONARY VEIN.
Answer:
first because that the first
