How many different original U.S. air dates appear where the U.S. viewers were 2.5 million?
CREATE TABLE table_25246990_5 (
    original_us_air_date VARCHAR,
    us_viewers__millions_ VARCHAR
)
SELECT COUNT(original_us_air_date) FROM table_25246990_5 WHERE us_viewers__millions_ = "2.5"
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: How many different original U.S. air dates appear where the U.S. viewers were 2.5 million? ### Input: CREATE TABLE table_25246990_5 (
    original_us_air_date VARCHAR,
    us_viewers__millions_ VARCHAR
) ### Response: SELECT COUNT(original_us_air_date) FROM table_25246990_5 WHERE us_viewers__millions_ = "2.5"