Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE student ( stu_num VARCHAR, stu_lname VARCHAR )
TABLE: CREATE TABLE CLASS ( crs_code VARCHAR, class_code VARCHAR )
TABLE: CREATE TABLE enroll ( class_code VARCHAR, stu_num VARCHAR )

### Question ###
What is the code of the course which the student whose last name is Smithson took?

### Accurate SQL ###

SELECT T1.crs_code FROM CLASS AS T1 JOIN enroll AS T2 ON T1.class_code = T2.class_code JOIN student AS T3 ON T3.stu_num = T2.stu_num WHERE T3.stu_lname = 'Smithson'