In controlled airspace, when the reported ceiling is 1,000 feet overcast and visibility is 3 miles, at what height must an aircraft join the circuit?

The correct choice regarding the procedure for joining the circuit in controlled airspace with a reported ceiling of 1,000 feet overcast and visibility of 3 miles focuses on the requirement for cloud clearance. When flying in controlled airspace, pilots must maintain specific distances from cloud bases to ensure safety and compliance with regulations.

Joining the circuit at 500 feet below the cloud base, in this case, means the aircraft would join at 500 feet above ground level (AGL). This is a standard practice that helps ensure the aircraft is clear of the clouds when entering the traffic pattern. It provides the necessary vertical separation from the cloud layer while also allowing for adherence to minimum visibility and separation regulations.

In this scenario, with an overcast ceiling at 1,000 feet, joining at 500 feet below that would position the aircraft safely at 500 feet AGL. This approach maintains compliance with visual flight rules (VFR) and enhances safety during the critical phases of flight, such as joining the circuit.

The other options do not align with the standard regulations regarding cloud clearance and circuit joining heights.