I believe the answer is D: <span>the treatment of slaves by their owners
Hope I helped! :)</span>
C. Archaeology is your answer
The American attitude shifted in favor of rights for Native Americans. This is based on "Polls showed that Americans believed in rights for Native Americans". Why it's not A is because it wasn't the polling that contributed to the act, but what the polls showed which is C.
The Flexible response was a policy implemented by President John F. Kennedy in 1961 in order to substitute the New Look and the massive retaliation policy that Dwight Eisenhower's had introduced, which consisted on responding using a greater force in case of an attack, and such force involved nuclear weapons.
On the other hand, the flexible response policy aknowledges the Mutual assured destruction if nuclear weapons are involved, as the enemy with shoot back too. It aimed to provide a manner of responding to agression across the spectrum of war but without the employment of nuclear weapons.
