In Class D airspace, what separation service is provided by air traffic control to participating aircraft?

1. All flights (IFR and VFR) are separated from each other at all times with standard radar minima
2. VFR flights are separated from other VFR flights, but receive no separation from IFR flights
3. No separation is provided to any aircraft; only flight information service and alerting service are provided
4. IFR flights are separated from other IFR flights and receive traffic information regarding VFR flights; VFR flights receive traffic information regarding all other flights