Question: What is the region 1 where region 4 is tba is the complete eighth series?
Schema: create table table_1337525_1 (region_1 varchar, region_4 varchar, complete_series varchar, PRIMARY KEY (region_1))
SQL: select region_1 from table_1337525_1 where region_4 = "tba" and complete_series = "the complete eighth series"