Amy is experimenting to see how a truss (a type of support) can strengthen a bridge. Amy builds several models of bridges out of toothpicks. Each model has a different number of trusses.

Amy suspends each model between two desks. She then adds lead weights to each bridge, one-by-one, until the bridge breaks. In the chart below, Amy recorded how many lead weights each bridge held before breaking.
What is a valid conclusion that Amy can draw from her experiment?