What should a building operator be prepared to do before sampling?

The correct answer is focused on the critical aspect of handling test results after sampling for Legionella. A building operator should be prepared to respond properly to the test results because the results can significantly impact the safety of the building's water supply and the health of its occupants. Depending on whether the test indicates the presence of Legionella bacteria, the operator may need to take immediate action, such as implementing control measures, notifying health authorities, or informing tenants of potential health risks.

Being prepared to respond appropriately ensures that the operator can act swiftly and effectively to mitigate any health hazards that may arise from the sampling process. This preparation can involve developing response plans in advance, understanding the implications of different test outcomes, and knowing the necessary steps to take for remediation and communication.

The other options, while they may seem relevant in certain contexts, do not address the immediate and critical need to respond to test results, which is paramount in the assessment and management of Legionella in plumbing systems.