When water is a product, the condensation reaction is often called a dehydration reaction. Condensation reactions are used to make crucial large molecules called macromolecules in the body, such as carbohydrates, lipids, and proteins. Carbohydrates are simple sugars such as glucose, which is used for energy in the body.
In a pH scale of 1 to 14, the smaller the pH is, the more acidic is. In opposite, the higher the pH is, the more alkaline it is. We call substances with pH below 7 as acid, and above 7 as alkali, while 7 as neutral.
Therefore, comparing the 4 solutions, solution a has the lowest pH, 3, so it is the most acidic.