I think that voter registration by the other 49 states is required because they want to control who can vote. C
If you could please expand and explain the answer you are looking for i will be glad to help you:)
I believe the answer is: C. A form of war emphasizing quick movement to take an enemy off guard
This tactic is one of the most successful tactic that is used by nazi's army during the world war II. With this, Hitler and his army managed to capture Paris with very little casualties, which lead to the disaster that had to be faced by the British Army on Dunkirk.