Final answer:
Congressional districts are reapportioned after each decennial US Census is completed to ensure equal representation.
Step-by-step explanation:
Congressional districts are reapportioned after each decennial US Census is completed to ensure that each district has nearly the same population. This process is necessary to avoid over or underrepresentation, also known as malapportionment.
Reapportionment occurs every ten years, and the boundaries of legislative districts are redrawn as needed to maintain similar numbers of voters in each district. It is done using the equal proportions method, which uses a mathematical formula to allocate seats based on U.S. Census Bureau population data.
Therefore, the correct option is C. Congressional districts are reapportioned after each census.