What is the region 1 where region 4 is tba is the complete eighth series?
CREATE TABLE table_1337525_1 (
    region_1 VARCHAR,
    region_4 VARCHAR,
    complete_series VARCHAR
)
SELECT region_1 FROM table_1337525_1 WHERE region_4 = "TBA" AND complete_series = "The Complete Eighth Series"
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 is the region 1 where region 4 is tba is the complete eighth series? ### Input: CREATE TABLE table_1337525_1 (
    region_1 VARCHAR,
    region_4 VARCHAR,
    complete_series VARCHAR
) ### Response: SELECT region_1 FROM table_1337525_1 WHERE region_4 = "TBA" AND complete_series = "The Complete Eighth Series"