Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_12722302_2 (original_air_date VARCHAR, us_viewers__million_ VARCHAR)
### Question:
What was the original air date for the episode with 3.90 u.s. viewers (millions)?
### Answer:
SELECT original_air_date FROM table_12722302_2 WHERE us_viewers__million_ = "3.90"