The first is true.
(A U C)={a1,a2,a3,....,c1,c2,c3,....}
(B U D)={b1,b2,b3,....,d1,d2,d3,....}
Cross Product those and what you end up getting is (AxB) U (AxD) U (CxB) U (CxD).
(This shows the Distributive property of cross product: (A U C)x(B U D)=(Ax(B U D))U(Cx(B U D))=(AxB) U (AxD) U (CxB)...