A pilot knows the pressure altitude. What correction gives the density altitude?

1. 1A correction for nonstandard temperature
2. 2A correction for wind and turbulence
3. 3A correction for instrument error and lag
4. 4A correction for the altimeter setting

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 4: Principles of Flight — Density Altitude, page 91