user: Question: Which young classification has an aggressive rider of Tim Johnson?
Columns: ['Stage (Winner)', 'General Classification', 'Young Classification', 'Sprint Classification', 'Aggressive Rider', 'Team Classification']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['0 Stage 1 ( Ivan Dominguez )', 'Ivan Dominguez', 'Nicholas Sanderson', 'Ivan Dominguez', 'Scott Nydam', 'Toyota-United']
SQL:

assistant: SELECT "Young Classification" FROM "Table" WHERE "Aggressive Rider" = 'Tim Johnson';