Answer:
The statement that summarizes the central idea of this speech from The Gettysburg Address is b): "The men who died have left an important task ahead to gain freedom for all."
Step-by-step explanation:
The speaker is saying that the ones that are alive, those who still can, should fight for the objective that the ones who died couldn't reach. They were fighting for a nation where "all men are created equal". That field must be a sign for those who live, the sign of the will of those who left everything in the battle in order to reach freedom and rights for the entire nation. The speaker feels that the ones who live have an important task to finish in the name of the dead and their own freedom.