The answer is going to be B. The native people lacked natural immunities.
The Europeans, having already been exposed to these diseases, had already built up their immune system to the diseases. The native people, on the other hand, had not been exposed to these diseases, and thus died because of it.
I believe the answer is B) The native people lacked natural immunities.
So for instance the small pox were something that were common throughout Europe and a lot of people were able to get and lose rather quickly because after a while, the body get's better knowledge of how to get rid of it. Unlike the natives who were far away and their bodies didn't have enough time to get rid of it.
A directly stated consitutional requirement in the US constitution in Article 2 Section 3 is that the President must give to Congress recommendations regarding the State of the Union and recommend any actions that are considered essential and expedient.