Table: dominik_meffert_tennis_stats
Columns: date
tournament
surface
opponent_in_the_final
score

Question: Who was the finals opponent on the hard surface tournament?
SQL: SELECT "opponent_in_the_final" FROM dominik_meffert_tennis_stats WHERE "surface" = 'hard'

Question: Which surface was played during Curitiba tournament?
SQL: SELECT "surface" FROM dominik_meffert_tennis_stats WHERE "tournament" = 'curitiba'