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_88 (class_from_1928 VARCHAR, class_to_1928 VARCHAR)
### Question:
Which class from 1928 had a class to 1928 of BDi-21?
### Answer:
SELECT class_from_1928 FROM table_name_88 WHERE class_to_1928 = "bdi-21"