user: Question: what is the polluntant when the regulatory citation is 40 CFR 50.7(a) and the type is Primary?
Columns: ['Pollutant', 'Type', 'Standard', 'Averaging Time', 'Regulatory Citation']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['SO 2', 'Primary', '0.14 ppm (365 μg / m 3 )', '24-hour', '40 CFR 50.4(b)']
SQL:

assistant: SELECT "Pollutant" FROM "Table" WHERE "Regulatory Citation" = '40 CFR 50.7(a)' AND "Type" = 'Primary';