What characteristic must the observer have during the operations?

The correct characteristic for the observer during operations is being independent. An independent observer is crucial in ensuring that their assessments and findings are free from bias or influence from those directly involved in the operation. This independence allows for objective evaluations of conditions, procedures, and safety measures, ensuring that the de-icing process is conducted effectively and safely.

The role of an independent observer is to provide an unbiased perspective that can accurately assess compliance with protocols and safety standards. This is especially important in critical operations, such as de-icing, where the potential risks of improper procedures can lead to accidents or operational failures. Being independent fosters trust in the assessment process and contributes to the overall safety and effectiveness of the operation.

The other described characteristics, while valuable in their own right, do not specifically align with the observer's role in this context. For instance, being dependable refers to reliability, authoritative implies a sense of power or control, and observant highlights the ability to notice details but does not encompass the critical aspect of maintaining objectivity that independence provides.