The state of matter that will have the least amount of density is c gas.
Density is defined as mass per unit volume. In general, solids are the most dense because the particles are packed closely together in a fixed arrangement. Liquids have a lower density than solids because the particles are still close but can move past one another. Gases have the lowest density because their particles are far apart and move freely. As a result, gases have much more space between their molecules compared to solids and liquids, which leads to a significantly lower density.