CREATE TABLE table_25795 ("Rank" FLOAT, "City/Town" TEXT, "County" TEXT, "Region/Province" TEXT, "Population" FLOAT, "Country" TEXT)

When 31901 is the population what is the county?
SELECT "County" FROM table_25795 WHERE "Population" = '31901'
SELECT "County" FROM "table_25795" WHERE "Population" = '31901'