To find the ratio of the minimum hourly flow to the average flow of sewage, we need to understand what these terms mean.

- Minimum Hourly Flow: This refers to the lowest amount of sewage flow that occurs within an hour. It represents the lowest point of flow during that time period.
- Average Flow: This refers to the average amount of sewage flow that occurs within an hour. It represents the overall flow rate during that time period.


To calculate the ratio, we need to compare the minimum hourly flow with the average flow.

Let's assume the minimum hourly flow is represented by "x" and the average flow is represented by "y".

The ratio of the minimum hourly flow to the average flow can be expressed as x/y.

According to the problem, the correct answer is option 'A', which means the ratio is 1/3.

This means that the minimum hourly flow is one-third of the average flow. In other words, the minimum flow is significantly lower than the average flow, indicating that there are periods of lower flow during the hour.


To further illustrate this concept, let's consider an example.

Suppose the minimum hourly flow is 10 liters per hour and the average flow is 30 liters per hour.

The ratio of the minimum hourly flow to the average flow would be 10/30, which simplifies to 1/3. This means that the minimum flow is one-third of the average flow.

This indicates that there are periods during the hour when the flow drops to 10 liters, but on average, it remains at 30 liters.

Therefore, the correct answer is option 'A' (1/3).