Which of the following relational operator(s) is(are) associative?

(This is a multiple answer question, the example of associative in arithmetic, (a + b) + c = a + (b + c)

	a.	DIVISION
	b.	DIFFERENCE or MINUS
	c.	UNION
	d.	- SELECT
	e.	SEMI JOIN
	f.	PROJECT
	g.	INTERSECT
	h.	CARTESIAN PRODUCT

Which of the following relational operator(s) is(are) commutative?

(This is a multiple answer question, the example of commutative in arithmetic, a + b = b + a)

	a.	PROJECT
	b.	DIVISION
	c.	CARTESIAN PRODUCT
	d.	- SELECT
	e.	SEMI JOIN
	f.	DIFFERENCE or MINUS
	g.	INTERSECT
	h.	UNION