Answer:
C. The legality of a state's voting districts.
Step-by-step explanation:
Baker v. Carr originated from a redistricting dispute in Tennessee, which had not redistricted since 1901. Previously, the Supreme Court refused to hear cases that were political in nature; however, the Court held that redistricting cases were justiciable (in other words, it could be heard by the Court) under a doctrine it had created to determine whether a case presented a political issue.