The answer is A.
Federal Laws that are against the constitution are not valid. Judges determine which laws are unconstitutional in the process of Judicial Review.
I'll first explain what the non-aggression pact was. It was an agreement that the Soviet Union and Germany would take no military action against each other. To answer your question it is B. The pact was to make sure he could safely attack Poland.
I would go D, anyone disagree?
