Under what condition can the basic gang rig, uncover, and cover hatches?

The correct answer highlights the operational efficiency and the specific conditions under which a basic gang is authorized to perform certain tasks, such as rigging, uncovering, and covering hatches. When only a basic gang is needed, it indicates that the workload does not require the full complement of specialized labor or machinery to carry out the tasks. This simplifies logistics and ensures that essential work continues efficiently without the need for additional personnel or equipment.

In contrast, specific instructions from a supervisor, the availability of machines, or the shortage of longshoremen do not inherently justify the actions of the basic gang. Those conditions might indicate different operational circumstances, but they do not directly empower the basic gang to perform these tasks independently. The emphasis on needing only a basic gang reflects the principle of maximizing labor effectiveness while adhering to contractual guidelines in the ILWU framework.