WHich Surface has an Opponent of gustavo kuerten?
CREATE TABLE table_name_13 (
    surface VARCHAR,
    opponent VARCHAR
)
SELECT surface FROM table_name_13 WHERE opponent = "gustavo kuerten"
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: WHich Surface has an Opponent of gustavo kuerten? ### Input: CREATE TABLE table_name_13 (
    surface VARCHAR,
    opponent VARCHAR
) ### Response: SELECT surface FROM table_name_13 WHERE opponent = "gustavo kuerten"