A is false. Because Epsilon is present in both, So their intersection can't be Null.
B is false.
LHS = (x + y + z)* = All the string over the alphabet x, y, z.
RHS, It is easy to see that it doesn't contain all the string over x, y, z.
C is True.
RHS = (p* q*)* = (p + q)* = All the string over the alphabet p, q.
LHS = (p + q)*p + (p + q)*q + $\epsilon$
$\Rightarrow$ LHS = (p + q)*(p + q) + $\epsilon$
The first part (p + q)*(p + q) contains all the string that is ending either with p or q. The second part contains $\epsilon$
Hence. It contains all the string over the alphabet p, q.
D is false.
$\sum$ * $\cap$ L = L.
So, (m + n)* $\cap$ (m + n)*mn = (m + n)*mn.