Which category provides ATC separation only for IFR aircraft?

The correct category that provides ATC separation only for IFR aircraft is Class E airspace. In Class E, air traffic control (ATC) is responsible for providing separation between IFR (Instrument Flight Rules) aircraft, ensuring safe distances between them, especially in congested or busy airspace.

While VFR (Visual Flight Rules) flights can operate in Class E airspace as well, they are not afforded the same level of separation by ATC unless the VFR aircraft is specifically participating in an ATC service, such as a VFR flight following service. This means that in Class E airspace, the primary focus for ATC is on IFR operations, prioritizing their separation from each other.

In contrast, other airspace classes like Class G are uncontrolled and do not have ATC separation services, whereas Classes C and D involve ATC separation for both IFR and VFR aircraft, depending on the traffic and the specific procedures in place.