Pressure altitude is the altitude read from the instrument when set to a barometric setting e.g 1013.25hp. This altitude does not factor ambient temperature. Density Altitude is the Altitude where the aircarft believes it may be.
In general, the density of the atmosphere decreases as altitude rises. It also decreases as temperature increases. A high density altitude doesn't mean high density. It means the density is such that the performance of an airplane will make the airplane think it's at a higher altitude. Regardless of the actual altitude (or elevation if it's on the ground), if the temperature is higher than a standard day, the density altitude will be higher and the aircraft performance will be lower.
Hope that it explains it! Answer is C.
