A is wrong
As double implication we need to check both sides and take a case where L1 is subset of L2 still intersection of the statement will be null.
Option B is wrong
because, take L1 as (a+b)*, now union of any non-regular language over alphabet a and b will always be regular.
Correct answers:
C and D
C is trivial and D is closure property where Regular languages are closed under both compliment and union.