CREATE TABLE table_50521 ("Nominative" TEXT, "Ergative" TEXT, "Dative" TEXT, "Genitive" TEXT, "Instrumental" TEXT, "Adverbial" TEXT)

What instrumental has chven-s as the adverbial?
SELECT "Instrumental" FROM table_50521 WHERE "Adverbial" = 'chven-s'
SELECT "Instrumental" FROM "table_50521" WHERE "Adverbial" = 'chven-s'