Question: With which association did Estribillo II run as Horse 1?
SQL: SELECT "Association" FROM "2-11951678-1" WHERE "Horse 1" = 'Estribillo II';

Question: Which horse was Horse 1 when René Guzmán raced with the Mulchén association?
SQL: SELECT "Horse 1" FROM "2-11951678-1" WHERE "Rider 1" = 'René Guzmán' AND "Association" = 'Mulchén';

Question: Who was the second rider when Papayero raced as Horse 1 in the city of Rancagua?
SQL: SELECT "Rider 2" FROM "2-11951678-1" WHERE "City" = 'Rancagua' AND "Horse 1" = 'Papayero';