Which measure type requires an aggregation method to be explicitly stated?

The measure type that requires an aggregation method to be explicitly stated is indeed the average. In Looker, when defining a measure as an average, it necessitates specifying the aggregation method because averages are calculations based on a set of values and need a clear definition to determine how those values are selected and combined.

In contrast, a count is inherently understood to aggregate by counting the number of records, thus does not require any additional aggregation method to be defined. The list type does not necessitate an aggregation method because it is used to display collected values directly without summarizing them in a singular aggregate form.

The choice stating "none of the above" does not hold true, as there exists a measure type with explicit aggregation requirements, hence it is vital to recognize the importance of specifying aggregation methods for computational integrity. The average measure explicitly necessitates that aggregation method be defined to ensure accurate data representation.