What is a pronoun antecedent agreement

A pronoun antecedent agreement has to do with keeping the consistency and inclusion of genders or lack thereof when writing. For example if you were to say "A student must call their parent/guardian before riding a different bus or she will not be allowed to ride said bus." you would be violating the pronoun antecedent agreement by saying she rather than they. 

answer: military leaders, supporters of the confederacy and supporters of the union.

explanation:

on november 19, 1863, the speech delivered by president abraham lincoln, known as 'gettysburg address', was intended for politicians, military officials, notable citizens as well as general public, and members of the press who had gathered for the ceremony held in gettysburg, pennsylvania. this ceremony was being celebrated since, in that same year, the battle of gettysburg took place in rural pennsylvania, leaving thousands of men, both union and confederate, killed. lincoln argued about equality within the nation, and the purpose of the war being a "new birth of freedom."on the other hand, there is no relation between lincoln's gettysburg address and his son.