Final answer:
Vinegar is known as acetic acid, which constitutes about 3-6% of its solution, and is created through the fermentation of apple juice or cider.
Step-by-step explanation:
The correct answer to the question "Vinegar is also known as" is A. Acetic acid. Vinegar is a solution that typically contains 3-6% acetic acid (CH3CO2H). It's produced by the fermentation of cider or apple juice in the absence of oxygen, where sugars present in the juice are converted to ethanol by yeast and then to acetic acid. Besides being a common household ingredient, acetic acid serves various purposes including being a solvent for organic and some inorganic compounds, and it’s essential in the production of cellulose acetate, used in synthetic fibers such as rayon.