What type of plumbing fixture would likely have a measured drainage unit?

A measured drainage unit is used to quantify the drainage flow capacity of plumbing fixtures, which helps in determining the necessary drainage systems and waste pipe sizes. In this context, a toilet is correctly identified as having a measured drainage unit because it plays a significant role in plumbing calculations related to waste and drainage systems. Toilets have a specific flow rate (gallons per flush) that can be quantified, making their impact on the drainage system predictable and manageable.

The other options, such as portable sinks, washing machines, and shower stalls, also produce waste but do not have the same standardized measurement for drainage units as toilets do. While these fixtures contribute to overall drainage, the toilet's drainage characteristics are more precisely defined within plumbing codes and regulations. This importance in planning and sizing for drainage systems highlights why toilets are specifically related to measured drainage units.