user: Question: What is the nationality of the event with a 1:51.51 time?
Columns: ['Event', 'Time', 'Nationality', 'Date', 'Meet', 'Location']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['50m freestyle', '20.91', 'Brazil', '18 December 2009', 'Brazilian Championships', 'São Paulo , Brazil']
SQL:

assistant: SELECT "Nationality" FROM "Table" WHERE "Time" = '1:51.51';