Answer
false
Work Step by Step
If $A\subseteq B$, then $A\cap B = B$
This is false.
$B$ is a superset of $A$ and can have elements that aren't in $A$. Those elements can't be in $A\cap B$, which means $A\cap B \neq B$.
It should say:
If $A\subseteq B$, then $A\cap B = A$
