Which command is used to remove a relation from an SQL?

DROP TABLE is the SQL command used to remove an entire relation (table) from a database.

Here's a breakdown of why the other options are incorrect:

DELETE: This command removes rows (tuples) from a table, but it doesn't remove the table itself.

PURGE: This command is not a standard SQL command. It might exist in specific database systems with particular functionalities, but it's not generally used for removing tables.

REMOVE: This is also not a standard SQL command for removing tables.

So, DROP TABLE is the correct choice for permanently deleting a table from a database.