Table schema:
CREATE TABLE Participates_in (actID VARCHAR); CREATE TABLE Activity (activity_name VARCHAR, actID VARCHAR)

Question: What is the name of the activity with the most students?
SQL: SELECT T1.activity_name FROM Activity AS T1 JOIN Participates_in AS T2 ON T1.actID = T2.actID GROUP BY T1.actID ORDER BY COUNT(*) DESC LIMIT 1