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_name_57 (gross_tonnage INTEGER, entered_service VARCHAR)
### Question:
Tell me the average gross tonnage for april 1919 entered service
### Answer:
SELECT AVG(gross_tonnage) FROM table_name_57 WHERE entered_service = "april 1919"