Which of the following SQL statements will return the year and average salary for all employees hire

Which of the following SQL statements will return the year and average salary for all employees
hired within a given year that have a salary greater than $30,000?

A.
SELECT * FROM t1
UNION
SELECT * FROM t2

B.
SELECT * FROM t1
UNION DISTINCT
SELECT * FROM t2

C.
SELECT * FROM t1
INTERSECT
SELECT * FROM t2

D.
SELECT * FROM t1
WHERE (c1,c2)=
(SELECT c1,c2 FROM t2)