CREATE TABLE table_55971 ("Nation" TEXT, "Gold" FLOAT, "Silver" FLOAT, "Bronze" FLOAT, "Total" FLOAT)

Which Bronze has a Nation of argentina, and a Silver smaller than 0?
SELECT AVG("Bronze") FROM table_55971 WHERE "Nation" = 'argentina' AND "Silver" < '0'
SELECT AVG("Bronze") FROM "table_55971" WHERE "Nation" = 'argentina' AND "Silver" < '0'