Which of the following is necessary for adding fractions?

Adding fractions requires finding a common denominator because fractions represent parts of a whole, and to combine them, those parts need to be of the same size. A common denominator allows for direct addition of the numerators while keeping the value of the fractions intact.

When fractions have different denominators, simply adding the numerators can lead to incorrect results, as you are combining different-sized pieces. By determining a common denominator, you can convert each fraction into an equivalent fraction that uses the same base, facilitating accurate addition.

Finding the least common multiple is part of the process to identify the common denominator, but it is not explicitly the step needed to add fractions, rather it's a means to reach the necessary common denominator. Converting fractions to percents and reducing them does not apply directly to the process of adding fractions and can complicate matters when the goal is simply to find a sum of the given fractions.