The correct answer is option 1: Acetic acid.

Vinegar is a sour liquid that is commonly used in cooking, cleaning, and as a condiment. It is made through a fermentation process that converts alcohol into acetic acid. Acetic acid is the main constituent of vinegar, giving it its characteristic sour taste and pungent odor.

Acetic acid is a clear, colorless liquid that is highly acidic. It is a weak acid, meaning it does not fully dissociate in water. This is why vinegar has a pH level lower than 7, indicating acidity.

The other options mentioned in the question are different types of acids but they are not the main constituent of vinegar. Ascorbic acid, also known as vitamin C, is commonly found in fruits and vegetables. Citric acid is found naturally in citrus fruits like lemons and oranges. Tartaric acid is found in grapes, bananas, and tamarinds. While these acids can be found in vinegar to varying degrees depending on the type, they are not the main constituent.

In summary, the main constituent of vinegar is acetic acid.