user: Question: What is Launched, when Laid Down is "31 October 1981"?
Columns: ['Ship', 'Hull Number', 'Laid down', 'Launched', 'Commissioned']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Nimitz', 'CVN-68', '22 June 1968', '13 May 1972', '3 May 1975']
SQL:

assistant: SELECT "Launched" FROM "Table" WHERE "Laid down" = '31 October 1981';