There are many possible answers for this one! Only the national government can e.g. manage foreign relations, declare war or oversee trade between states and with other countries.
I am pretty sure that the following which was the main benefit to the spread of disease in the New World for the colonists is being revealed by the option : “Limited number of Natives available to fight back against the colonists”. I choose this one because that was the point which led Natives to show their weakness and captured by the colonists.
Hoope it helps!
Christianity or majority catholic?