Answer
As a senator, Sergio Osmeña represented the 10th senatorial district, which comprised the provinces of Cebu, Bohol, Leyte, and Samar. This district was established under the 1935 Constitution, which divided the Philippines into 12 senatorial districts, each electing two senators. Osmeña's representation of this district reflected his strong ties to the Visayas region and his commitment to representing the interests of its people.