To determine the maximum hourly consumption, we need to consider the factors that affect the water demand in a city.

Factors Affecting Water Demand:
1. Population: The size of the population directly affects water demand. As the population increases, so does the water demand.
2. Residential, Commercial, and Industrial Activities: Different sectors have different water demands. Residential areas typically have a higher demand compared to commercial and industrial areas.
3. Climate: The climate of a city also impacts water demand. Areas with hotter and drier climates generally have higher water demands due to increased usage for irrigation and cooling purposes.
4. Water Conservation Measures: The implementation of water conservation measures can reduce water demand in a city.

Given Information:
- Annual average hourly demand of the city = 10000 m3

Calculating Maximum Hourly Consumption:
The maximum hourly consumption can be estimated by considering the peak water demand in the city. This peak demand can be influenced by various factors, such as the time of day and specific events or activities.

Since the question does not provide any specific information about these factors, we can assume that the maximum hourly consumption occurs during the busiest time of the day, when all sectors are using water simultaneously.

Assuming a conservative estimate, we can consider a peak-to-average ratio of approximately 2.7. This means that the maximum hourly consumption is 2.7 times the average hourly demand.

Therefore, the maximum hourly consumption = 2.7 * 10000 m3 = 27000 m3

Conclusion:
Based on the given information and assuming a conservative peak-to-average ratio, the maximum hourly consumption of the city is 27000 m3, which corresponds to option A.