To remove all rows from a table in SQL, you can use either the DELETE statement or the TRUNCATE statement. The correct SQL syntax for these operations would be 'DELETE FROM t1' and 'TRUNCATE TABLE t1'. The DELETE statement removes all rows from the table but logs each row deletion individually, which can be slower for large tables. The TRUNCATE statement, on the other hand, is more efficient as it does not log individual row deletions and instead logs the deallocation of the table's data pages. Therefore, the correct answers are using 'DELETE FROM t1' and 'TRUNCATE TABLE t1'.