user: Question: What is Opinion Research Centre (OPC), when Party is Conservative?
Columns: ['Party', 'Marplan', 'Gallup', 'National Opinion Polls (NOP)', 'Opinion Research Centre (OPC)', 'Harris']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Conservative', '41.5%', '42.0%', '44.1%', '46.5%', '46.0%']
SQL:

assistant: SELECT "Opinion Research Centre (OPC)" FROM "Table" WHERE "Party" = 'Conservative';