What must the pilot do if they cannot concur with the clearance?

When a pilot cannot concur with a clearance, it is essential for safety and operational integrity that they notify Air Traffic Control (ATC) immediately. This communication is crucial as it allows ATC to understand the situation and make any necessary adjustments to the flight plan or instructions. The pilot may have concerns about safety, compliance with regulations, or the technical capabilities of the aircraft.

Proactively informing ATC allows for a resolution that can ensure the safety of the flight, as well as the safe management of surrounding air traffic. It also helps to prevent misunderstandings that could lead to dangerous situations in the airspace. Engaging with ATC ensures that the pilot is not navigating on their own accord, which might inadvertently lead to conflicts with other aircraft or airspace restrictions.

The other options, while they may seem like alternatives, do not prioritize immediate communication and collaboration with ATC, which is the most critical action to take in such scenarios.