(a)

A\\\\cup B=B\\\\cup A

\ (b)

A\\\\cap B\\\\cap C=C\\\\cap B\\\\cap A

\ always true\ always true\ sometimes true\ sometimes true\ never true\ never true\ (c)

(A\\\\cap B)^(')=(B\\\\cap A)^(')

\ (d)

A=A^(')

\ always true\ sometimes true\ always true\ never true\ sometimes true\ never true\ (e)

A\\\\cup C=A

\ (f)

A\\\\cup B=B\\\\cup C

\ always true\ sometimes true\ always true\ never true\ sometimes true\ never true

(a) AB=BA (b) ABC=CBA always true sometimes true always true sometimes true never true never true (c) (AB)=(BA) (d) A=A always true sometimes true never true always true sometimes true never true (e) AC=A (f) AB=BC always true sometimes true always true never true sometimes true never true