CREATE TABLE table_73723 ("Stage" FLOAT, "Winner" TEXT, "General Classification" TEXT, "Youth Classification" TEXT, "Mountains Classification" TEXT, "Sprint Classification" TEXT, "Most Courageous" TEXT, "Team Classification" TEXT)

Who won the mountains classification when Maarten Tjallingii won most corageous?
SELECT "Mountains Classification" FROM table_73723 WHERE "Most Courageous" = 'Maarten Tjallingii'
SELECT "Mountains Classification" FROM "table_73723" WHERE "Most Courageous" = 'Maarten Tjallingii'