user: Question: What is the Riding, when the Rank is 4th?
Columns: ['Riding', "Candidate's Name", 'Gender', 'Residence', 'Occupation', 'Votes', 'Rank']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Central Nova', 'Michael Mackay', 'M', 'West River Station', 'Retail', 427.0, '4th']
SQL:

assistant: SELECT "Riding" FROM "Table" WHERE "Rank" = '4th';