Katherine needs to cut a piece of cardboard for an art project at school. She has four pieces of cardboard that she can cut from 6 inches, 5 inches, 7 inches, and 3 inches. If the length of the cardboard she needs is square root 35 inches, which piece of cardboard should she cut to create the least amount of unused cardboard?
3 inches
5 inches
6 inches
7 inches