Which of the following is a temporary alternative measure when a boom length indicator malfunctions?

When dealing with a malfunctioning boom length indicator, marking the boom with measured marks to calculate the boom length serves as a practical temporary workaround. This method allows the operator to have a reference for the boom's lengths based on predetermined measurements, thereby enabling them to still operate the crane while adhering to safety protocols that involve understanding the boom's extent.

This approach is particularly useful because it allows for continued operation without compromising safety, assuming the operator is proficient in the crane's capacities and can accurately use the markings to avoid exceeding limits. It ensures that the operator can visually reference the boom's position concerning safe operation parameters.

While other solutions may seem viable, they generally involve either stopping operation, which is not as flexible as marking the boom, or relying on alternative systems that may not be available or tested to be reliable under the current circumstances. Marking the boom provides an immediate and effective solution to assess the boom length for the tasks at hand, facilitating the ongoing work process while addressing the malfunction.