user: Question: What's the PM for the standard with 12.3 g/kWh CO?
Columns: ['Standard', 'Date', 'CO (g/kWh)', 'NO x (g/kWh)', 'HC (g/kWh)', 'PM (g/kWh)']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Euro 0', '1988–1992', '12.3', '15.8', '2.6', 'none']
SQL:

assistant: SELECT "PM (g/kWh)" FROM "Table" WHERE "CO (g/kWh)" = '12.3';