user: Question: What was the nationality of the swimmer in the Semifinal with a time of 29.51?
Columns: ['Event', 'Date', 'Round', 'Name', 'Nationality', 'Time', 'Record']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ["Women's 50m breaststroke", '12 December', 'Heats', 'Rūta Meilutytė', 'Lithuania', '29.56', 'CR']
SQL:

assistant: SELECT "Nationality" FROM "Table" WHERE "Round" = 'Semifinal' AND "Time" = '29.51';