The correct answer is D) A positive, but not linear relationship.
This comes from the equation Ek=1/2mv^2
Where Ek is Kinetic Energy, m is mass, and v is the speed (or velocity).
As we can see in the equation, the relation is not linear but quadratic and it is positive.
It would be very difficult to argue that one person/event can accurately summarize the huge political, social, and economic changes that took place during this era. One must consider that this time period saw the anti-war movement, civil rights movement, environmental movement, and parts of the women's rights movement. No one person or event involved all of these different changes at once.
However, if you were to make this argument you could use the following:
a) Martin Luther King Jr.- His role in the Civil Rights movement and peace movement make him one of the biggest civil rights icons of the 21st century.
b) March on Washington for Jobs and Freedom- This 1963 march included hundreds of thousands of Americans and allowed MLK to give his "I have a dream speech."
The legal challenges contribute to the decline of Reconstruction when President Lincoln announced that there is a plan for reconstructing the Confederate states which are already under the Union control. He proposed to excuse the Confederate who took a pledge to support the Union.
Because a civil war is war happening within the same country, hence the literal name.