Well..as far as i learned from my knowledge the answer would be in the past, the military and the FBI have prevented a number of terrorist attacks.
Secondly, wasn't there suppose to be an option answers for your question ?
Answer:
D ( Native Americans were susceptible to European diseases and many died)
NO we faught back!! Thats how we entered WW2.
New factories in germany put people out of work this is a social reason for migration
