A. Perhaps names will be forgotten, but the sacrifice for freedom will always be appreciated.
Explanation:
Option A is the concept that both speeches have in common.
In Martin Luther Jr's speech, he revealed that it is those that were willing to suffer for righteousness' sake that are to be remembered by men and women of the land. The righteousness' sake he refers to here is "the sacrifice for freedom" many of them made.
Abraham Lincoln's speech shares the same thought with Martin Luther King Jr's speech. In Abraham Lincoln's speech, he reveals that the dead can only be remembered not be forgotten because of what they have done.
Methinks already from this chemic flame, I see a city of more precious mould: Rich as the town which gives the Indies name, With silver paved, and all divine with gold.