user: Question: What is the class with 1 quantity?
Columns: ['Class', 'Railway number(s)', 'Quantity', 'Year(s) of manufacture', 'Type']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['BW', '1–5', '5', '1887–1900', 'A1 bm']
SQL:

assistant: SELECT "Class" FROM "Table" WHERE "Quantity" = '1';