From which of the following three areas are samples generally collected?

Samples in drinking water systems are typically collected from key stages in the water supply process to ensure the safety and quality of the water being delivered to consumers.

The first area, the raw water supply, refers to the initial source where water is collected, which could be surface water like lakes and rivers or groundwater from wells. Testing at this stage is crucial to identify the natural quality of the water and any potential contaminants before it undergoes treatment.

The second area is the treatment plant, where raw water is processed to remove impurities and make it safe for consumption. Samples taken here are essential for monitoring the effectiveness of the treatment methods employed and ensuring compliance with health regulations.

Lastly, sampling from the distribution system is vital as it checks for potential contamination that might occur as water moves through pipes to reach consumers. This location helps evaluate the overall integrity of the water supply system.

By sampling these three areas - the raw water supply, treatment plant, and distribution system - water quality can be comprehensively assessed, allowing for effective management and remediation of any issues that may arise throughout the water supply chain. Other options, while they may include valid locations for sampling, do not encompass the entire process in a way that reflects the critical points of monitoring throughout the supply chain.