What tournament was held on 21 May 2006?
CREATE TABLE table_78351 (
    "Outcome" text,
    "Date" text,
    "Tournament" text,
    "Surface" text,
    "Opponent" text,
    "Score" text
)
SELECT "Tournament" FROM table_78351 WHERE "Date" = '21 may 2006'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What tournament was held on 21 May 2006? ### Input: CREATE TABLE table_78351 (
    "Outcome" text,
    "Date" text,
    "Tournament" text,
    "Surface" text,
    "Opponent" text,
    "Score" text
) ### Response: SELECT "Tournament" FROM table_78351 WHERE "Date" = '21 may 2006'