user: Question: Which original operator is in the 25NC class?
Columns: ['NBR number', 'Year', 'Original operator', 'Class', 'Wheel arrangement', 'Road number', 'Location']
Types: ['real', 'real', 'text', 'text', 'text', 'real', 'text']
Sample row: [22880.0, 1922.0, 'New Zealand Railways', 'A B', '4-6-2', 745.0, 'Stratford']
SQL:

assistant: SELECT "Original operator" FROM "Table" WHERE "Class" = '25NC';