CREATE TABLE table_71757 ("Date" FLOAT, "Category" TEXT, "Team" TEXT, "Rider 1" TEXT, "Rider 2" TEXT)

Which category earlier than 2006 has Bart Brentjens as rider 2?
SELECT "Category" FROM table_71757 WHERE "Date" < '2006' AND "Rider 2" = 'bart brentjens'
SELECT "Category" FROM "table_71757" WHERE "Date" < '2006' AND "Rider 2" = 'bart brentjens'