The answer to the question is Carbon dioxide
The process that occurs in a cell when there is not enough oxygen
is called fermentation. Fermentation occurs through the process of Anaerobic Respiration,
where instead of using oxygen, organic and inorganic molecules are used as
final electron acceptors. The by-product of this process is usually alcohol,
ethanol, or acetic acids.
<span>
Fermentation is commonly used in lactic acid (in muscles) and alcohol (beers,
whiskey) fermentation where the by-product is ethanol. Yeasts are a common
organism that uses this process, where it convert sugars into alcohols or
acetic acids.</span>
I'm assuming you mean the molecular compound

and it's name is Hydronium. Hope this helps :)
id say the first one and the third one, sorry if it’s wrong
The correct answer is A.) however C.) is cellular respiration or the function of the mitochondria. D.) is describing chloroplasts B.) is something concerning DNA and proteins synthesis