what is the polluntant when the regulatory citation is 40 cfr 50.7(a) and the type is primary?
CREATE TABLE "standards" (
  "pollutant" text,
  "type" text,
  "standard" text,
  "averaging_time" text,
  "regulatory_citation" text
);
SELECT "pollutant" FROM "standards" WHERE "regulatory_citation"='40 cfr 50.7(a)' AND "type"='primary';