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_21716139_1 (train_name VARCHAR, category VARCHAR, frequency VARCHAR)
### Question:
What trains have a category of express and a weekly frequency?
### Answer:
SELECT train_name FROM table_21716139_1 WHERE category = "Express" AND frequency = "Weekly"