user: Question: When Mark Cavendish wins sprint classification and Maarten Tjallingii wins most courageous, who wins youth classification?
Columns: ['Stage', 'Winner', 'General Classification', 'Youth Classification', 'Mountains Classification', 'Sprint Classification', 'Most Courageous', 'Team Classification']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Mark Cavendish', 'Mark Cavendish', 'Alexander Kristoff', 'Paul Mach', 'Mark Cavendish', 'Maarten Tjallingii', 'Team HTC-Columbia']
SQL:

assistant: SELECT "Youth Classification" FROM "Table" WHERE "Sprint Classification" = 'Mark Cavendish' AND "Most Courageous" = 'Maarten Tjallingii';