CREATE TABLE table_5999 ("Stage" TEXT, "Winner" TEXT, "General classification" TEXT, "Points classification" TEXT, "Mountains classification" TEXT, "Combination classification" TEXT, "Team classification" TEXT)

Which Mountains classification has a Team classification of quick step?
SELECT "Mountains classification" FROM table_5999 WHERE "Team classification" = 'quick step'
SELECT "Mountains classification" FROM "table_5999" WHERE "Team classification" = 'quick step'