Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_73723 ( "Stage" real, "Winner" text, "General Classification" text, "Youth Classification" text, "Mountains Classification" text, "Sprint Classification" text, "Most Courageous" text, "Team Classification" text )

### Question ###
Who won the mountains classification when Maarten Tjallingii won most corageous?

### Accurate SQL ###

SELECT "Mountains Classification" FROM table_73723 WHERE "Most Courageous" = 'Maarten Tjallingii'