Question: What stage (winner) has Thor Hushovd as a general classification, and Trent Lowe as a rider classification?
SQL: SELECT "Stage (Winner)" FROM "2-15683301-18" WHERE "General Classification" = 'Thor Hushovd' AND "Young Rider Classification" = 'Trent Lowe';

Question: What stage (winner) has Quick Step as the team classification, and Trent Lowe as the young rider classification?
SQL: SELECT "Stage (Winner)" FROM "2-15683301-18" WHERE "Team Classification" = 'Quick Step' AND "Young Rider Classification" = 'Trent Lowe';