To which type of element can a Tableau associate apply a default aggregation?

A default aggregation can be specified for a measure, making A correct. Measures represent quantitative values and are normally aggregated when they are added to a visualization. For example, a Sales measure typically appears as SUM(Sales). Tableau allows the author to change the measure's default aggregation so that subsequent uses of the field can initially use AVG, MIN, MAX, COUNT, standard deviation, or another supported aggregation instead of SUM. The configuration is available from the Data pane by right-clicking the measure and selecting Default Properties > Aggregation. The choice becomes the default behavior when the field is subsequently added to a view, although the aggregation can still be overridden for an individual instance of the field. Dimensions do not use a default measure aggregation in this manner because their primary role is to partition and categorize the data. Bins are generated categorical fields representing numerical intervals. An already aggregated calculated expression also has restrictions because Tableau cannot arbitrarily aggregate an expression that is already defined at an aggregate level. Tableau's official Default Settings documentation specifically states that users can specify a default aggregation for any measure and documents the Data pane workflow for configuring it.