Which of the following statements is true regarding flight operations and ATC service in Class A airspace?

1. Only IFR flights are permitted, and all flights are provided with air traffic control service and are separated from each other.
2. Both IFR and VFR flights are permitted, and all flights are separated from each other.
3. IFR and VFR flights are permitted, but VFR flights only receive traffic information in respect of other VFR flights.
4. Only IFR flights are permitted, but separation is only provided between IFR flights and known VFR flights.